So over on the superb boardgamegeek.com there’s a long list of free computer implementations of boardgames. This is a great resource and there’s plenty to choose from, from old classics like risk to more recent games like settlers of cataan. Many of these are windows only, but just as many are browser or java based and thus run on all platforms. A few I’ve played and enjoyed include Pioneers (a settlers of cataan clone), SpaceHulk-SP, Invade Earth (a risk 2210 AD clone), and Heroquest, an amazingly complete clone of the old Heroquest dungeon adventure game. There’s tons more at the link above and the chances are good that there’s a board or card game to your taste.