Dropbox for cloud storage across all your devices. Put an Excel file into your Dropbox folder on your desktop PC and voila! It's on your iPhone, iPad, etc.
Netflix - their mobile app is really good IMO.
Soundhound for identifying songs you hear on the radio.
TripIt if you travel a lot. It organizes your itineraries, flight info, rental car, hotel, etc
Last edited by jetstream23; 01-16-2013 at 11:32 AM.