I don't like to pay for my MMO's either so I've played Runescape which I don't recommend, Rappelz, Conquer 2.0, and Shaiya. Rappelz was OK and I don't reccommend Conquer. I currently play Shaiya, and it is the best of all free MMORPGS that I've played. It really is a cooperative game.
If you'd like to know more about Shaiya then post on my profile and add me. If you decide to play it then I'd add you.