Guild wars: I seem to remember having to use cedega (rather than wine) to play on amd64, worked well.
Price ~$50 per expansion
Description: Diablo 3 Online
Commentry: Wanted to play with my board gaming group, brother, and gf. Didn't work out so i'm not playing. I enjoy it, it's technically quite good, and will play again if i can convince friends to join me.
World of Warcraft: Worked well with wine, you may need to refer to the howto in this forum.
Price ~$50 + $15 per month
Description: Diablo 2 3D online, Warcraft world and warcraft 1 pathfinding, coupled with diablo 2 network lag.
Commentary: Not playing any more due to loot lock (bag lag?), and high erratic pings from Australia making skilled play very difficult. Expensive. Artistically very good for such a graphically low-spec game. I spent too much time playing this. I'll happily play again if there is a local server.
Wurm Online: Worked native, but i think needed some mucking around with x86 sun java to get it to work on amd64.
http://www.wurmonline.com/
Price: Basic is free
Description: Um. Maybe like playing a sim game crossed with a FPS? I didn't play enough to know, try and see?
Comments: I only tried it briefly due to frame rate issues. And only before it went gold. It allows a lot of interaction with the world, and appears to be driven by personal goals rather than a story and events to follow. If you break computer games up into story, game, and toy. this Wurms tends to (complex) toy while GW and WoW tend to story.
I'll test it again if i can get playable performance.
Utopia: text based web browser MMOG
Price: Free
Description: Text war game. Train and send armies to take land from those weaker than you, thieves to take gold, mages to do nasty stuff to them and helpful to you. Help your kingdom do the same.
Comments: I stopped playing Utopia and similar games because i couldn't manage the time commitment. Similar games include Dominion and Battlemaster (which is graphical enough to have a map). Good points include that you can actually interact violently with other players unlike GW and WoW, and that they can be played from anywhere.
Nation States: web browser game. sort of MMOG
http://www.nationstates.net/cgi-bin/index.cgi
Price: Free
Description: amusing government simulation game.
Comments. Well worth playing around with for a few weeks until it gets repetitive. I haven't tried participating in the multiplayer aspects, but last i played there was no war. Originally built as advertising for a book which i also found worth reading. Every now and then i play it again for a bit to see the new events.
I'm going to have to take a closer look at vendetta, thanks for mentioning it.