I store all my photos on Flickr. Until a few weeks ago, they had a nifty little built-in photo editing program called Picnik. For some insane reason, the wizards at Yahoo decided to kill off Picnik and to replace it with this useless piece of crap, Aviary. Seriously, don't even try it. It will just make you mad. You can't straighten photos (which was my primary use for Picnik) - you can only rotate by 90 degrees.
You also can't zoom in to see what you are editing. So if you need to remove a blemish on someone's face, well, good luck with that.
The good news is that the Picknik folks have a new, free, service called Picmonkey. It is much like Picnik, only even more charming and cute. The only problem is that you have to edit photos first and then upload to Flickr, which I constantly forget to do.
You can do all kinds of magic and tragic things to your photos. Slap on a couple filters, and voila. The whole world is dipped in an unearthly vibrance. I don't know if I like it or hate the end product below, but I'm having fun.