2. Sports Radio Droid
3. Beautiful Widgets
6. SetCPU and Rom Manager (They go hand in hand lol)
8. Root explorer
9. Battery left widget
10. Cachemate for Root Users
Yeah, descriptions of what the apps do would be nice.
Wikidroid/IMDB - quick and easy wikipedia/IMDB search apps. Faster than the browser for me.
Droidlight - turns your LED on to use as a flashlight
SportsTrack Live - uses GPS to track my daily runs. Records distance, speed, elevation change. Can keep track of previous runs on their website
Chicago Transit Tracker Pro - tracks buses in Chicago and estimates arrival times
ICE: In Case of Emergency - puts emergency info on my Droid screen when anyone turns on the screen, in case I'm injured or unconscious and they need to know blood type, who to contact, etc. Works with lock screen.
Google Voice - Google stores my voicemail and transcribes them to text
Google Maps/voice nav - stock app, but really helpful nonetheless. Navigate for me as I drive places I'm unfamiliar with.
Facebook for Android - easy to use facebook app
Not Call Log - automatically brings me back to home screen after a phone call so I don't accidentally pocket dial. Also, convenient since I usually don't want to be on the call log screen after a call.
Wave Secure, Mobile Defense - WS can remotely lock/wipe/back/restore your phone if it's lost or stolen. MD can use your phone's GPS to send you location information on a lost or stolen phone.
In no particular order:
Sirius XM Radio (requires paid subscription...free app)
Pandora Radio (requires free account. Free app).
Flycast Radio (edit. I use it for WEEI Sports Radio only). Beta. Free. Got it from flycast.com iirc. To my knowledge, it's not on Market. Radio streaming app.
ESPN Radio. Paid app
Facebook for Android. Free app.
GMail stock app
Email stock app
Tapatalk Pro (paid app)
Twitter for Android
Opera Mini Beta. Free app.
Definitely my most used along with Calendar
EDIT: thanks to the OP and several of you for your lists. Several of these were just added to my phone.