I just started Runes of Magic. It's FREE and the gameplay/graphics is very comparable to WoW.
Actually I enjoy this game more.
Also, if you're looking for some single player fun check out Minecraft. (Not quite MMO) It's very addicting, but not free.
You get your own world and can mine and build anything out of anything. There are monsters which try to kill you too.
There are tons of free MMOs out there. Lord of the Rings Online has gone free recently and the graphics are not bad, but I just don't like LoTR so I deleted it. If you like turn based games where you get your own party of character classes (in a MMO!) check out Atlantica Online.