I'm constantly on the lookout for free/cheap online photo editing programs. Editing photos can make a good photo great, a bad photo good. Whether you are just adjusting colors or changing the style, photo editing is the major difference between professional and amature looking photos.
When I had a computer, my go-to was just iPhoto. I never had the money or time to get Photoshop, so free and easy is what I need. I'm not trying to do anything fancy, mainly adding vingettes or changing a color pic to black & white, so iPhoto worked well. I eventually downloaded Poladroid for a faux polaroid look. And Photobucket's FotoFlexor program works pretty well, except that its so slow. I liked Rollip alot until they started charging for their edits.
But yesterday, farting around, looking for something comperable to iPhones Hipstamatic app, I found Picnik. It's free, easy, and fast!!! You can instantly publish your photos to Twitter or Facebook. I'm thinking of upgrading to the premium version ($24.99 for 1 year) because I like it so much. Here is a photo I was playing with.
Original photo, no edits
added vingette, and "lomo-ish" effect.