Runes of Magic is a free MMO that is basically a free alternative to WoW. Its just about to come out of beta. It differs from WoW in a fe ways though. You can have 2 classes for one character at level 10 you gain your second class. Classes are switched by talking to your House Maid from inside your house.
I am a Knight/Priest. With my class set to Priest I can use a limited number of Knight skills and visa versa. Each class has to level seperately. So im 10/11. Each combination creates a unique class and at certain levels (15,20..[i forgot the rest]) you will get skills that are a combination of abilities from both classes. Class combinations create unique classes that are good for certain things eg.
Knight/Priest = tank
Priest/Rougue = Insane DPS :S
Screenshot:
The download is 3.4 GB and after that it patches which takes around an hour.
Heres a guide on how to register as its a bit weird:
http://forum.runesofmagic.com/showthread.php?t=38074and the link
http://runesofmagic.comIm on the EU/UK servers realm called "manachat" or something.