I'm boring. I use mostly the following:

Facebook
MapQuest
Kindle
Fruit Ninja (really stupid time-suck game)
Sudoku
Runkeeper (GPS device for tracking my runs)
Junos Pulse (VPN app to access my work network from anywhere)

I also have recently installed and only started working with:

ScanBizCards - where you scan a business card and it puts it into contacts for you
BookHabit - Keeps track of books you read - I haven't even begun playing with this one yet
Rotate&Crop - to crop photos I took with the iphone before posting to facebook or somewhere else
TreeID - to identify trees when I travel but I haven't used it yet


And my calendar, notes and contacts from Outlook sync.