Instagram / Hipstamatic
Why you need it: By now you should be familiar with the Internet-age adage: Pics or it didn’t happen. Want to make all your Twitter followers jealous? Snap as many pics as you can and put ‘em through a cool filter using one of these two apps. Hipstamatic will run you two ducats, but you’ll get more, and better, filters than Instagram which is free.
Download Instagram from the Apple App Store, Free
Download Hipstamatic from the Apple App Store, $2