GeneRally is a freeware top down racing game. You can drive all kinds of cars or vehicles on all kinds of of tracks and surfaces like tarmac, gravel, mud, sand, ice, grass etc.
Download a free copy of the game on the official website (find in Links).
The best thing about the game is, that you can design your own racetracks and cars with included or external standard applications.
The trackeditor gets installed with the game - just try it!