SSSD 0 Light Poster

Hi, just recently playing mmos on my pc, namely 'fusionfall', graphically it is a good game but it is very slow. So i was wondering if there are any other browser based mmos you could recommend? i dont want to download anything as my computer is slow enough already!
Not looking for runescape or anything, that game looks rubbish. Preferably 3rd person, and also free.

Additional info
MMO - massively multiplayer online (game)
Browser based - No download