BB 8330
Aside from the standard loaded ones, I've installed and pretty much only use these:
Opera
Viigo - News and RSS Feeds (weather, sports, stocks, etc)
WebMessenger
Myspace
Tip Calculator
Google Maps
Documents To Go
QuickPull - Reboots Blackberry w/o having to take out battery
Handmark Blackjack
I use all of these on a daily basis. Any other good ones to add to my list you think? Let me know.