rFactor is the best game around, IMO. You can only buy it online ($40 at rfactor.net), but well worth it. The basic game is for F1 racing, but there are so many mods it'll make your head spin. Hell, they even have a lawnmower racing mod. The only thing I haven't found yet is a midget mod, but there are sprints, and somewhere upwards of 30 dirt tracks.