Over the course of many Android installs to my Nook Color I've refined my list of what I consider the absolute minimum set of apps you need to maximally enjoy the platform and compensate for some of the peculiarities of this device in particular. This list should also serve as a useful list for those with other Android devices.
Must Have Apps
Without these apps your experience will be a little painful (unpleasant, limited, frustrated, and potentially dangerous).
Adobe Flash (Adobe Flash Player 10.3)
iPhone and iPad may be too “good” for Adobe's Flash but Android isn't, and thank goodness for that. Download this free app and you'll now have Flash available in your browsers! When you load a page which contains an embedded Flash widget you'll see a little download icon in the box. Click the icon and the Flash content will download and run. Now you can experience the entire web on a tablet! While Flash generally works great, with a few skipped frames in video here or there, some sites like Hulu won't work. You can download special modified APKs found in the various sites like XDA-Developer to work around these mobile limitations; those versions of Flash fool the Flash into thinking they are being run on a desktop/laptop computer.
Easily Access your SD card from your PC (Only Needed on SD-Based OS Installs) (USB Mass Storage Utility)
The best thing about having so much storage on an open platform like the Android is being able to use it, and for most of us using it involves transferring data to and from our computer. If you're booting with an SD-based OS you'll probably find that the built-in feature allowing you to share your SD files over USB no longer works as expected. Thankfully, a genius over on xda-developer, samuelhalff, has created an app to solve this problem! You just need to download and install (on your Nook) the apk file from the link I'll give in a moment. Getting the apk on your Nook can be done most easily in two ways, a) using the Nook Color go to the link in a browser and click the file, I believe it will let you install it directly, depending perhaps on which browser you use, or b) use File Expert and its SMB plugin to access a Windows file folder on your computer. One it's installed, run the app, choose what you want to mount. You can choose between physical partitions or protected spaces (like ROM, cache, etc.). And if you need you can mount up to two things at a time using the tabs at the very top. In the case of the verygreen CM7 install, if you want to expose the SD card partition you choose "Mount SD(4) Fourth Partition".
NOTE: As the warning in the app says, make sure you safely eject the mounted drive before you disconnect or you might lose all the changes you made (he makes it sound like a "definitely will" not just might). Also, the app renders itself for a phone sized screen, so you can run disable the compatibility mode as he suggests or merely view in portrait and scroll down with your finger to find the "CONFIRM" button you must hit to start the mounting.
Required for Bluetooth Keyboard Users (Null Keyboard)
If you're a Bluetooth keyboard user you've probably discovered it's no joy to use one on Gingerbread (CyanogenMod). When you type on your Bluetooth keyboard the virtual keyboard will very likely appear, or re-appear if you've hidden it. You close the keyboard, you type, maybe it stays closed for a moment or two, but invariably it opens up again. And, because it's open not only do you have much of your screen real estate wasted by a keyboard you're not using, your physical keyboard presses will often linger long enough to pop up the Android (Gingerbread) character selector. In other words, type "e" on the keyboard and about 5% of the time it will think you held "e" down in order to bring up the list of international "e" variations, a dialog you then need to close. And, as if that's not annoying enough, the predictive text completion that will go on with the virtual keyboard open will lead to sometimes sluggish responses to your keypresses, and even text that gets lost. I discovered the solution is to install Null Keyboard. It costs $2, but it's money well spent. You install it, enable it in settings, and then when you are going to use your BT keyboard you hold your finger down on an input box for a few seconds, it asks you to choose your input method, you choose Null Keyboard, and voila! You can now type on your BT keyboard with joy. And when you put away the keyboard don't forget you'll need to switch the input back to your Android (or Gingerbread) keyboard next time you need to type with the virtual one.
Managing Files, Managing your System (Super Manager, Ghost Commander, File Expert, Root Explorer)
There will be times when you need to do maintenance on your little tablet computer. You may need to move files around, perform basic maintenance, kill processes. For file operations you've got several great choices.
Ghost Commander is a great app for doing file operations, but its interface is clearly borrowed from a 1990's console app; you can't beat the features, but Steve Jobs would weep if he had to use it. Ghost Commander is built to make copying/moving files easy, with its side-by-side dual pane/location display. And, with the SMB add-on, you can access Samba/SMB/Windows shares.
File Expert is a step up from Ghost Commander on the UI front, and has a lot of great features, but it's not as ideally suited to transferring files. What truly sets File Expert apart from Ghost Commander or Super Manager (discussed next), and the only reason I use it, is that it is the only app in the Market which lets you stream/play audio and video content. (It temporarily buffers to the SD card and launches the requisite app to do the playing.) With an SMB add-on you can access Samba/SMB/Windows shares.
Super Manager is a beautiful collection of amazingly useful tools, from file management, to task killing, to backup. An absolute must-have! (But, it's not ideally suited to moving/copying or playing files.)
Root Explorer is another great file system explorer, but it's not free, it's a pricey app at $5, but worth it if you need what it offers, including built in: text viewer, SQLite database viewer, tar/gzip, execute scripts, remount, permission changer, send files (bluetooth, email), and more.
I recommend you download and install all the free apps since that will cover you, and if it's relevant to you the SMB plug-ins you might need. And if you need more, Root Explorer is a good investment.
Better Browsing (Dolphin Browser HD)
The built-in Android browser is lousy. It is intended for use in a phone and thus it has few features, few options, and many websites seeing the type of browser you are using dumb down their site as a result. Firefox's app in the Market is little better. Fortunately there is a free browser that truly gets the tablet space. It includes every feature you want, and many you don't yet realize you want; some of these features come via free add-ons you can find in the Market.
Once you get the Dolphin Browser HD I strongly recommend you also get the Dolphin Desktop Toggles which lets you control whether the remote websites see you as a mobile user or not.
Anti-Virus (Antivirus Free by Creative Apps)
Recently much news was made about malicious and thieving Android apps. While the risk in general is minimal, it's always a good idea to be protected. Antivirus Free has the best ratings and reviews in the Market and, as the name suggests, is free. I'm a little dubious about its effectiveness since the maker, Creative Apps, doesn't have an established pedigree when it comes to anything anti-virus, but here's two fingers crossed they know what they're doing. Anti-Virus Free by AVG is another solution.
Backup your Apps (Titanium Backup)
You should back up your apps and their data from time to time. This is critical down the road when it comes time to migrate to a newer Android version (Honeycomb). Titanium Backup (free version) will allow you to make backups and you can then move these backups to your home computer and then restore them to your new OS in the future.
Optional (but recommended) Apps
These are apps I find reasonably invaluable, but you are entitled to your own ridiculously ignorant view of the universe.
Quick Access To Needed Things (Widgetsoid2.x)
You will need easy access to some very basic things on the Nook Color. You will need easy access to brightness settings, wifi settings, orientation lock, and volume settings (if you remapped the volume keys). The best way to give yourself easy access to these things (and many others) is with this amazing little app which creates completely customizable widgets on your Home screens. My Home Screen 1 widget is a 4x1 widget including brightness cycler (cycles through 4 settings), sleep prevention toggle (keeps my tablet on when I need it to be, otherwise the screen and wifi shut down after 1 minute), orientation lock, volume adjustments, and battery indicator. My Home Screen 2 widget is a 4x1 which includes data sync toggle, speaker on/off, wifi settings shortcut, and reboot. Configure this now, if you like.
Controlling your CPU and Battery Life (CPU Tuner)
CPU Tuner lets you control how your processor is used, with profiles (different CPU operational limits) assigned to various triggers (different battery charge levels), so you can balance performance with battery life. Once you overclock (further down) you'll use this to set your new limits. With CM7 this is not required, you can set the CPU limits in the Settings > CyanogenMod 7 Settings. But, it's a good app and you may wish to try it.
Next Generation Keyboard (Keyboard from Android 2.3+)
This is the only non-free app in this list, and it's well worth the $0.99! CM7 has the new Gingerbread keyboard, but this app has added some really nice features into the keyboard, like easily accessed directional cursor keys! I highly recommend this app! Seriously, it's a buck, the time you save in typing in just your first day is worth at least that!
Obviously you can add more apps at this point, but these are the basics you'll want to make sure you have before proceeding.
Notion Ink Apps (Quick Office, Sniffer, etc.)
Someone has extracted and repacked some the great apps that come with the popular and innovative Adam device, you can download them outside the market via an xda-developer post. I personally haven't found the Notion Ink apps all that useful with the notable exception of Sniffer and the bundled Quick Office. But I may be alone in my lack of amazement, the apps appear quite popular. Sniffer tells you about your Android device, memory, disk space, and lets you explore the file system and the processes; the layout, not really the features, make this compelling. Other Notion Ink apps include one for drawing, an email alternative, a calculator replacement, a calendar replacement, and a browser replacement (that appears not to work properly on the Nook Color). One truly compelling addition is Quick Office, one of the best of the office suite apps that lets you create and edit Word documents, PowerPoint presentations, and Excel spreadsheets. It appears this has all the features of the version sold in the Market. I am a little confused about whether or not these apps, Quick Office in particular, is being legitimately redistributed here. No one seems to say it's not, and so I'm not sure if it is under some sort of GPL/LGPL or something that allows it. If anyone knows any different let me know and I'll remove this link.
These are apps which deserve mention, but are either too buggy, or have too limited an audience to spend time describing in detail.
Gmail Notifier shows an alert in the status area / pull down letting you know who just emailed you. It sadly doesn't seem to do a pop-up overlay which would have been nice. I couldn't find one that did.
WinAmp is what I'm using for Shoutcast streaming and some MP3 playback, but it confoundingly doesn't seem to run in the background when playing regular MP3s.
DoubleTwist is what I'm using for MP3 playing in the background. I know there are a bunch of other audio/video apps I need to try out, I've heard their names a bunch but it's just not been what I've focused on so far. I'll update this list when I get into it.
JustPictures! is a great photo viewer which includes support for all the popular remote photo hosting sites (e.g., Flickr).
PlayOn is amazing, if you run the PlayOn server on one of your home PCs. With this and its TVLinks plugin I can watch anything anywhere.
Rhapsody is how I stream all my on-demand music.
ClockworkMod obviously deserves a mention, but I didn't because a) it won't run on my setup so I've not been able to dive into it, and b) it's already installed as part of most of the installs.
QuadrantStandard is what everyone uses to benchmark their Android devices.
SD Tools is a great way to test your SD card reading/writing speeds.
Tapatalk is your best option for browsing discussion sites, it parses those sites beautifully and then gives you a great tablet experience with all the features you'd expect (except forum specific searching!).
Sleep Timer is good for listening to music and then having it stop the music after a while.
Wapedia is a great Wikipedia interface.
WordPress is a tolerably basic way to update your WP site on the go.
No Longer Required
These apps were absolutely required, until CM 7 included their features, I'll leave them here in case anyone doesn't like the way CM 7 implemented the similar feature set.
Virtual Hardware Keys (Button Savior)
This is a must for Nook Color users. CyanogenMod 7 has a really cool feature built in, it places your missing Back and Menu buttons in the top status bar. This works flawlessly except when an app goes full screen! In those cases you need something, and that's where Button Savior steps in. It's a much more elegant solution to my mind than its popular competitor, Softkeys. You can still map the volume buttons to the Back/Menu keys, as I covered int the Froyo guide, but since you'll use the status area buttons most of the time, I find volume buttons are more important and that compensates for the slightly indirect way I have to sometimes use the Button Savior virtual keys.
Remove the Lock Screen (No Lock)
The “lock” screen you see whenever you turn on Android makes perfect sense in the context of a cell phone, but it's a nuisance if you are using a tablet. You can download and run the free app “No Lock” to disable the lock screen (as well as re-enable it when it's required).