Sonic Central: The official site
Sonic HQ: More Sonic information than you could shake a stick at.
The Sonic Stadium: A huge Sonic site by a rockin' British dude.
Sonicanime.net: Sonic X fansite.
Team Artail: Lots of artwork.
Chao Flight Path: Cute Sonic art.
Sonic the Comic Online: A fan-continuation of the Fleetway Sonic comic.

Chapapanga.org: My main site.
Organized Chaos!: My mixed fandom fansite.