I'm sure no-one else has mentioned these so: Firstly I'd suggest you try Rusty Hearts, it's a great game (think Devil May Cry meets Streets of Rage, kinda direction... sorta), and the (on the EU servers anyway) community is quite nice too.
Also while not entirely so WoW is free until Level 20. (with a somewhat serve feature stripping) It's more of a really large (15GB-ish) demo, than a free game. Still worth a look if you want to get into it though.
Also try Toribash, that game is fun too! And having a knowledge of real martial arts can actually help you in that one! The community is a bit eh, but go in positive and everyone else seems to just fall into the same mindset too. This one is a fast download, and probably falls more into line of what you're thinking about when you said free games.
I hope this helps!