TrackMania - The most popular online PC racing game.
Real Racing - Experience all of the excitement, competition and glory of championship racing.
TORCS - TORCS, The Open Racing Car Simulator is a highly portable multi platform car racing simulation.
SuperTuxKart - 3D arcade-style MK-like kart racing game
Forza Motorsport - Microsoft Games Studios published a great game named as Forza Motorsport is a Racing, Single, and Multiplayer video game.
Stunt Rally - Stunt Rally is a racing game with rally style of driving, mostly on gravel.