try Adventure Quest or Wonderland Online.... i stuck with them for pertty long before i get bored and leave... both of them are free with optional premium item.
Mir 3 Global was the game i use to play but got way to addicted got to lvl 56 on a tao Post Merge: [time]1271785744[/time] Rapplez and Shiya are 2 other games that i will put my Thumb Up For
DDO just became free. It's quite a well balanced game with a decent community. Silkroad-online is an excellent free MMORPG, the only problem is it can suffer from lag issues depending on what time you log in to play.
I second Grand Fantasia, I've played a few F2P MMORPG's and it's probably the one I stayed with the longest, though atm I'm playing WoW which is F2P for me ;D because my bro pays for my account ;D.
Allods Online is pretty fun as well. It's as close to WoW without saying it's WoW. It's also got some nice game mechanics, like charging up spellcasts, random effects using the same school of magic for mages...whatever else I haven't figured out yet. I'm not that far. I like that is has its own mechanics for "cartographer," "questhelper," and all that built right in. No addons needed and I've got pretty much everything I need. Oh, and Priests are hella sweet being able to wear plate at the end. And I just googled a melee-based healer. Retri-fricking OP paladin anyone? So far, I'm liking the spellcasters best.
Gaia Online's zOMG! Ragnarok + Private Server Phantasy Star Online + Private Server Tales of Pirates Mabinogi The Endless Forest