Fauxto is a neat little photo/picture editing program, free for use and entirely online. It runs using Flash (pretty much ubiquitous nowadays) and has all the regular tools you might expect for picture editing plus a few nice effects and filters.
It’s multi-layered and sits somewhere between MS Paint and a cut-down version of Photoshop (Elements I guess?). Since it’s all online, you’re always running the latest version and the developers seem quite active.
Well worth taking a look if you need a quick and handy photo editing program.