Saw this on Twitter posted by @GAME_Offers and thought I'd share. Shame I paid £50 on launch.
The Forza 3 Limited Edition comes with:
Forza Motorsport 2GB USB Storage and keychain.
Forza Motorsport VIP Membership* and Exclusive Car Pack: Includes special treatment within the online Auction House, Community Storefront and on the Forzamotorsport.net forums, plus 5 of the hottest cars from the roster of Forza Motorsport 3.
Exclusive Collectors Edition Car Pack: Includes 5 cars that have been hand tuned and hand painted by the developers at Turn 10 to fly the Forza Motorsport colours.
Exclusive Forza Motorsport 3 Theme: for customising your Dashboard!