Stumbled across this today
.: SUMO Paint :.
Flash based online photo editor thats very Photoshop-esque. For a browser based app its surprisingly quick on my 1024/512 connection so any higher than that and it should be quite good. Has a lot of tools and the main features of Photoshop, quite impressive.
I think its limited to 50 uses then you'll be asked to upgrade to a pay service but I think if you changeyour IP and clear cookies it might work again.