photoshop
if it is after the fact then i suggest only this...
or download the Photoshop app from the app store.. or go here..
http://mobile.photoshop.com/ipho…
instagram. square view when you take the photo, and you can choose to add no effects.
Instragram is okay. I'm not so big on the whole sharing side of it though.
Plastic Bullet
http://itunes.apple.com/us/app/p…
Camera+ has a square Crop built in...