I've now tried many of my favorite android apps from my EVO (still testing many more, believe it or not), but here are some of my personal must-have apps that mostly seem to work on the NookColor (no oddities noticed yet, but I haven't tested every single feature in every app, enough functionality exists for me to want to use the app). Some of these are pay apps or associated with subscription services -- I already bought them for my EVO, so no extra charge for me. Yes, some of these are repeats in this thread. I've tried to link to the free version where one exists, but if the link is a pay app, doublecheck before buying whether a demo version exists (I could have missed it).
UTILITIES
AppBrain -- android app manager and good frontend to the Android Market. syncs to online service. You can keep lists of apps you want, manage different devices, track upgrade available. Links in this message are to appbrain so you can tag the apps for download to your device, then open appbrain on your NookColor to download (they have an autodownloader but I don't use it). I almost never go direct to the market anymore, only through this app as a gateway.
QuickBoot -- Quick access to reboot and power down functions (remember to hide the recovery and bootloader options so you don't mistakenly press them)
Terminal Emulator -- Allows you to enter android command line commands, use only if you know what you are doing
aLogcat -- displays the log file and allows you to email it to someone (good for helping devs debug apps)
Titanium Backup -- backup your apps
MoreRecent -- shows most recent 15 apps (good when you run lots of apps).
Root Explorer -- Allows you to manage the root file system, use only if you know what you are doing.
Speed Test -- latency and bandwidth tester from speedtest.net
SystemPanel -- system monitoring tool, good for identifying bad apps that use up your battery
Wifi Analyzer -- shows you the wifi access points around you, how strong they are and what channel they are running on.
Battery Indicator -- puts a percentage indicator in your bottom bar showing how much battery is left.
Home Switcher -- Lets you see what launcher apps you have installed, set a default or launch any of them. Good for switching back to stock launcher if you want it.
Button Savior -- docks a tab on the side to allow you to access standard android buttons in any app.
Gesture Search -- a must have once you have dozens or hundreds of apps. Just start writing the letters of the app you want on the screen. From Google
Astro -- Good all around file and app manager
LogMeIn -- Very good and reliable remote PC access program -- I help manage my parents' computers from across the country with this. Also enables me to log in securely to my desk PC when I forget something from home. Expensive, but I've used this widely cross-platforms and mobile devices for years.
INTERNET SERVICES
Dolphin Browser HD -- full-featured browser alternative. I love the gesture-based shortcuts and plug-in options.
LastPass for Dolphin Browser HD -- works with LastPass and allows you to auto-fill web passwords securely.
LastPass -- app for premium LastPass.com subscribers. Manage your web passwords securely. Also has a good security audit program online to make sure you aren't using duplicate passwords at important sites and rates the quality of your passwords. Here is the interface for android.
Huffington Post -- decent front end to this liberal news site
FML -- frontend to the random time-waster FML website when you are standing in line with nothing else to do.
OpenTable -- frontend to opentable.com. Make reservations on the run any time.
Evernote -- frontend to evernote cloud document storage -- all my docs are available on-demand for viewing. Add and edit notes anytime.
MUSIC:
AudioGalaxy --allows you to stream your entire music collection from your PC and (usually) is able to read itunes playlists (some issues there, and they are working on it).
Rhapsody --Subscription streaming service -- I use this on my home Sonos system as well
Pandora --Customizable radio stations, learns your preferences.
Slacker --Another customizable radio station service
Andronos -- Remote control for Sonos users (only useful for those with Sonos house music system).
GAMES AND MEDIA
Aquarium Live Wallpaper -- free and donation versions. Excellent aquarium screensaver. I have mine set to complete black with no accessories and a single turtle that floats around my screen.
Turtle available in 0.99 donation version.
Enjoy Sudoku -- Awesome, awesome version of this game. Is a training program as well, will take your sudoku skills to the next level. Can be set to to get rid of tedious aspects of game and let you focus on pure logic. It is even smart enough to use the full tablet screen, giving you two number pickers in portrait mode (one for selection, one for pencil notes) -- Wow.
Picasa Tool -- Want to access your picasaweb albums? Here you go.
JustPictures -- I'm playing with this -- I want a good slideshow so I can 'dock' my Nook and have it be a picture frame this is the current contender.
UinU -- fun little logic game
SketchBook -- very full-featured drawing app. A bit of learning curve, but has layers and all.
Flight Director -- landing planes game.
Roku Remote -- For those of you with a Roku player at home. Acts as a remote for your device.