So I have been a windows 7 only user for the past few years, and with lion and my new air, I'm really enjoying the mac os again. Since I bought my new air on a student purchase, they gave me a $100 app store gift card and since I don't have an iPhone or iPod touch, I really don't know what in the world to do with it. I rarely buy music on iTunes.. The app store is overwhelming to me since I haven't really used mac apps in a while and sure I could just let my 100$ credit just sit there till I notice something, but that could take a long time... In your opinions, what are the most useful/fun apps on the app store?