Frets on Fire - Website with the latest version and links to information community documention and resource sites. Make sure you check out the forum, its where you'll find most of the FOF fanatics making constant mods and new songs.

Frets on Fire Wiki - Massive amounts of info on every Frets On Fire topic including a huge song database.

Personal Songs Database - Decided to go thru the ol' music collection and convert it to FOF playable files (my wife loves this game).