A friend of mine sent me a beta access code for Mythos, a soon to launch free Diablo-type game from Flagship Studios. The game was built to test out the online tech for Flagship's first large title, Hellgate: London.
The game is cute and fun. It features hack and slash in it's purest form, but unlike Dungeon Runners (another free to play Diablo Clone), Mythos doesn't try and mock the hack and slash genre.
It is fun when you have a few minutes to kill, but I don't see it replacing anyone's main game anytime soon.
Update: 9 May, 2009 - Removed broken link and updated labels.