You can download TrackMania Nations Forever for free!
Download Mirrors:
Filefront
GamersHell
Peliplaneetta.net (Finnish link)
Worthplaying
ComputerGames.ro FAST!
Internode
Freenet.de (Duke's link )
Steam FAST! (If you have problems with the Steam version, read this topic.)
Clubic (French link)
Jeux-Video.com (Direct ftp link!) FAST!
Jeuxvideo.fr (French link)
Jeuxvideopc.com (French link)
Factornews (French link)
When/if you find new download links (especially fast ones), post them here so I can add them to the list.