Here's the apps I use regularly on my droid -

Droidlight (turns the LED flash on/off like a flashlight)
Togglewifie (wifi on/off toggle button)
The weather channel
Pandora
Advanced Task Killer
Missed Call (reminder buzzes/rings if you miss a call or text)
Flixster (movie times & tickets)
Astro file manager
Speed Dial

Random apps that are cool to play with:
Android lightsaber
Barcode Scanner
SchottGunn
Stopwatch