With Picnik you can quickly edit all your online photos from one place. It's the fastest, easiest way to fix underexposed photos, remove red-eye, and apply special effects to your photos ~ from artsy to comical.
Compares many of the most well-known photo sharing sites, although it seems to have missed Fotki. Fotki is a top notch site, and deserves to be in any list of top contenders.