Hey, anyone here ever heard of Fallen Sword? It's a browser-based MMO that costs nothing to play.
I've been playing it for over a month now and I have to say it's pretty good. The graphics (what little there are) are fine and the gameplay is simple yet compelling. You don't have classes or anything, so the abilities you do have are based solely around who has the better weapons and armor. There are skills to learn, guilds to join, and a constantly expanding gameworld.
It's probably a bit archaic to those used to more glamor from their MMO, but I think it makes a nice diversion when you're too busy for a real game.