iBooks was another Apple addition to the iTunes store with the iPhone 4 launch this year and it hasn't disappointed. The iBooks app turns your device into an e-reader that allows you to buy best-sellers or classics (some of which are free) and have them downloaded directly to your iPhone. The app lets you flip through a book with a finger swipe, as well as bookmark pages and take notes in the margins. Your library is kept in an easy-to-navigate virtual bookshelf.
Price: Free via iTunes