As far as i can tell, right now the BEST, cream of the crop f2p mmorpgs are:
1) Runes Of Magic - this game is as close to WoW as you can probably get without being sued. Literally. If you like wow, you will love this.
2) Dungeons & Dragons Online - formerly a subscription game. It failed, died, and was resurrected as a F2P game, where it now enjoys immense success. Probably the first Western-made MMO to try the F2P model and succeed.
3) Atlantica Online - turn based MMORPG. You command a party of yourself and up to 8 "mercenaries" in final fantasy style turnbased combat.
4) Perfect World International - formerly the gold standard of f2p mmos, as the games get better, it slides further and further down the list.
all of which are free to download and play.
on the horizon there is Allods Online, which will raise the bar for f2p games. And the original designers of Diablo are working on a Diablo-style MMO called Torchlight.