a great game is found here : http://www.medievia.com . before just closing your browser tab though, read through a little, and before completely dismissing the game go to http://solidsun.com/cm/ and then connect to the game (directions are on the homepage).
it's a real deep game, if you like warcraft and starcraft and strategy games like that you can really get into medievia.
Medevia used to be a big hit in our support department. We were actually hosting the server that ran that MUD. I wonder if we still do. I never played it on my Mac or got to involved in it.