I have sooooo many apps I can reccommend:
1. iTalk lite - this is a voice recorder that is WAY better then the installed iPhone app. You can name you recordings in the app, choose the quality/file size and wirelessly transfer the recordings to your computer... all of which you can't do on the origonal app. It's free too! This has been an AMAZING study tool for recording lectures. Now instead of reading hundreds of text and scrambling to take perfect notes in class, I get some "skeleton notes" in lecture then re-listen to the lecture and "re-fine" my notes thus learning only the important topics.
2. Orange or Apple Flashcards- this is a great flashcard tool... much better then all the other apps in the store and cheaper (i think only a dollar or two). You can enter the flashcards in by hand through the app or through excel or any spreadsheet program. Row a is side one and Row b is side two, so you just cut and paste your notes into excell, copy them to a page on the companys website then wirelessly transfer them to your phone. Takes only 20-30 mins to create awesome flashcards that can be viewed in landscape, finger swipe flips the card and goes to different ones and your can suffle them, repeat ones you got wrong and so much more. VERY USEFUL
3. Anatomy and Drug pronuncations - For 3 dollars each you get perfect recordings of the correct way to pronounce those impossable drugs... so cool. They have a free version too but once you use it, you will want to buy the full version.
4. Med Calculator - nuff said, it's free too.
Those are the main ones I use