VDrift - VDrift is a cross-platform, open source driving simulation made with drift racing in mind.
Stunt Rally - Stunt Rally is a racing game with rally style of driving, mostly on gravel.
TORCS - TORCS, The Open Racing Car Simulator is a highly portable multi platform car racing simulation.
Speed Dreams - Speed Dreams is a 3d cross-platform, open source motorsport simulation and racing game.
SuperTuxKart - 3D arcade-style MK-like kart racing game
TrackMania - The most popular online PC racing game.