16. WriteRoom
Amazingly, the iPhone comes with no way of syncing text files and its Notes app stinks. This simple word processing tool transfers text easily between desktop and handset so you can leave your laptop at home. $4.99

17. Amazon Kindle
The Kindle's nice, but why carry two devices when you can download e-books directly to your phone? Have an iPhone AND a Kindle? Once you've bought the book, you can read it wherever you want. Free

18. Cheap Gas
Pretty straightforward—shows you the least expensive petrol wherever you are. Awesomely helpful if you don’t know the area. Free

19. Babelingo
Great linguistic value—300-entry phrase book with 11 languages for just $3.99.

20. Where
Shows you what’s around you, from Starbucks to movie theaters and show times. Free