In my series of Linux game reviews, I come to TORCS: The Open Race Car Simulator. It is a 3-d racing simulator with a great variety of tracks available and decent graphics. If you are looking for a casual racing simulator, this is a good one. The physics simulation is good, and the large selection of tracks means there is something for everyone. You can race a high-speed oval, a road course, and anything in between -- including tri-ovals and rectangular tracks.
Before you start playing, tinker with the user controls. Personally, I find the default steering sensitivity to be unusable and drop it dramatically. Like all racing simulators, it is best played with a wheel and pedals, not a keyboard. Unfortunately, all I have is a keyboard.
Though certainly worth a little time, TORCS is for the casual racing fan and is not up to par with commercial offerings. It is fun for awhile, but if you have played any of the recent NASCAR simulators you will be a bit disappointed in TORCS. There is no way to customize your car's mechanics in the shop, the graphics do not include spectators, logos, or weather, and no matter what you do the controls will be a bit choppy. In its current form, it is more of an arcade game than a realistic simulator. That is not necessarily bad -- it is, after all, a good game -- but you may need to manage your expectations.