TORCS
If you want a powerful racing game, look no further than TORCS, The Open Racing Car Simulator. It’s gone from a 1997 2D soapbox derby simulator to a powerful 3D racing game with championships, tons of tracks, a thriving community, and all the third party tracks and cars you can download.

VDrift
Want realistic racing? Then you need to try VDrift. First released in 2005 by Joe Venzon and inspired by Gran Turismo, Venzon created a simple racing game powered by the Vamos Automotive Simulator. Two years, three programmers, and a ton of code later, it’s got extremely realistic physics, 28 cars, 19 tracks, AI players, networking, and great looking graphics.

[VIA]