Great apps, screened for you, by me:
Instapaper - I mentioned this one
before, but decided it deserves it's own official listing since I find it so useful! This great app allows you to "bookmark" articles online and moves them to the app's own list for reading later. It has greatly cleared the clutter of newspapers/magazines that I would save for the one or two articles I hadn't read. It's pricey, but worth it (especially with my crazy schedule, I can read on the subway!) There is a FREE version if you want to try it out first.
iCam (WebCam Video Streaming) - Wow! I can't say enough about this app. I've been looking for an inexpensive way to monitor my apt. It's fun, but also just offers peace of mind. Some people use it to monitor their pets at home while at work. It works from your laptop camera, webcam, or other external camera. It even detects motions, sends push notifications to your iphone if movement is sensed (you can set the sensitivity of movement), and records pictures when movement is sensed. It's pretty amazing! If you're looking for a cheap way to monitor whatever is going on at home, this is a great, inexpensive solution!
Ride the City - I love cycling (non-competitively) and this app is great for mapping out routes from point A to B. I've been a fan of ridethecity.com for a while and find it's pretty accurate. Costs ya a bit however, at $2.99
Spokes NYC - Very similar to Ride the City. There are pros and cons for both, but I prefer this map interface over Ride the City. And, this one is FREE! Now if I could somehow get either one to allow me to save frequent routes!
NYC BikeMap - Brought to you by the same Spokes NYC people, this is pretty handy. They need to update to the 2010 map, however. Again, FREE!
MyClasses - Yep, I'm a geek! I like to keep track of how I'm doing in a class and this app does the job. The UI leaves a bit to be desired as it takes a bit of patience to navigate and set up classes. But once you know what you're doing, it's not so hard. Keeps track of your GPA and your classes, even calculate weighted assignments/tests. Not bad for $1.99.