What Apps do you suggest I purchase with my iTunes card? (see details)

I bought a MacBook Air, so Apple is going to email me a $100 App Store gift card. It might just be a iTunes gift card, so I may be able to get a couple movies too.

Anyways, I’m in University so I want to mostly get apps that will make my academic life easier. Any great apps that you would suggest for me? Tell me why it is so awesome, and what it does.