(I get bored with radio stations a lot, but if you switch between these three ^ you hear more of a broad selection.)
enver RTD (has local bus schedule, nearest bus / train stops, can route your path for you based on GPS, etc)
Advanced Task Killer
I haven't found a TON that I use, but there's really not much else I use my phone for besides music, communication, and GPS.
I've got an app that turns the camera light on so my phone can be used as a flashlight, but I don't have to use it often. The Mint app doesn't handle my new credit union, so it looks like I'll be starting work on developing an app that syncs GNUCash on my local computer to a small interface for my phone. I tend to not balance my checkbook by hand. Ever.