Still, this thread is very useful for people who are looking for free (quality) MMOs.
Granado Espada (http://ge.iahgames.net - another English version of Sword of the New World but without it's watered down gameplay and crippled costume system)probably is the best one right now. It is, however, still officially Beta and the business model has yet to be announced.
Whether it will be f2p, b2p or p2p is not certain, but some kind of hybrid model (probably similar to Cabal Online) has been implied by the Devs.
GE has some refreshing features, like controlling 3 characters at the same time, leveling a whole family (up to 36 characters) with family level giving advantages to every single character - paradise for Alt-O-Holics.
Gameplay is a bit repetitive and grind-only, customizing is non-existent and the world is split into several really (really) small maps. Furthermore, every map has a specific level range (e.g. 64-68). So the gameworld is linear sequence of small maps.
Still, with it's sweet eye candy, perfectly realistic and fluid animations, original scenario (a bit like the good old Arcanum, a mixture of fantasy, baroque and pop culture; but controlling a chick with dreadlocks, a shining plate armor, cowboy boots and a musketeer-rifle can be quite cool) and the ability to "play" the game while being afk, it's probably the best f2p game currently available.
Anarchy Online has been mentioned here, but I wouldn't really call it one of the best f2p games out there.
Thing is: The "full" Anarchy Online, despite it's severely outdated graphics engine, is one of the best and most elaborated MMOGs ever made. No doubt.
The f2p-version, however, lacks most of the content (most of all Shadowlands, an expansion which is more like a whole new game than just an expansion). All you can do is doing the random indoor-missions over and over again. Not being able to ever be competitive, missing out most content and fun and, and, and...
Tantra is another nice one. Haven't played it for too-long, since I got hooked up by GE. Some issues: It's officially played on Filippino servers, so most players speak Tagalog only (or a weird mix of Tagalog and English). Also, the Item Mall contains some very game-breaking stuff. If you would like to *really* get into the game and be competitive, you would have to spend some real life cash on the overpriced stuff.
I am generally not very fond of cash shops that lead to a the-one-with-more-rl-money-owns-you server-societey.
Guild Wars is not really f2p but b2p. Still, it beats all the titles here.
It does, however, lack the feel of persistent world and a real MMORPG. Hopefully, GW2 will fix that.