Y-Corner

Focus Home, the creators of the TrackMania racing games series, has made TrackMania Nations Forever freely available for download on their website.

http://www.trackmania.com/en/index.php?lang=en&rub=nations

This is the full, entire game, which includes a lot of solo tracks. This game also includes full blown online play as well, which is a nice perk.

If you're looking for a racing game, you might want to check this out.