Dolphin browser HD- so far my favorite browser.
Folder Organizer- although there are other similar apps that I haven't tried.
Angry Birds- the first game I've liked in 20 years.
Droid Light or MotoTorch LED - emergency flashlight.
Reddit is fun - because it is.
Android IRC or AndroIRC - nice to have IRC access, whenever, wherever.
QR Droid - QR codes decoded and generated.
Bar Control - when you need to play with your notification bar.
Dilbert - got to have Dilbert.
Google Earth, Google Sky Map, Google Services, Google Goggles - all sorts of Googley goodness.
Vignette - when stock camera apps don't do it all.

I'll add more when I get more time.

I really like ES File Explorer as a file manager.

As for games, Bubble Blast, angry birds, jewels, unblock me free and slice it.
Misc.. Catch Notes, Compass, ringdroid, winamp beta

Yes, I agree with Matt, ES File Manager is a very helpful file manager. Easy to get to look at all files, including the SD card within a single app.

ben wrote:

Android WiFi Analyzer,
a must have if you want to survey an area with your phone

Thank you for sharing that app, I will have some fun scanning areas with it.