I just have to recommend Grand Prix Legends.
Yep, it is dated October 1998, but as it turned out this simulation (don't call it a game please) could be extended with extra tracks and graphics.
Online racing is a blast as well. I run in three online leagues myself and I must say it is quite addictive.
Have a look at these links for more info:
http://www.vroc.net/
http://magnust.d2g.com/
http://www.racesimcentral.com/
http://gplea.racesimcentral.com/
http://gplpp.com/
http://gplrank.schuerkamp.de/php-pub/lc_ranking.php?option=showall
There are a lot more, but these should get you started.