Picture from picnik via Flikr

horsing around 140, originally uploaded by Beanie76.

Picnik is an online photo editing tool. You can get photos from other places like your computer or Facebook etc. then work on them. It wont store your photos though so you have to send them to Flikr or Facebook, Twitter, Myspace etc. or back onto your computer.
It would be usefull in a pedagogic sense as it allows students to be more creative with their photos or slideshows then send them onto other areas for storage and input into discussions or group work.