SMS Power The best site on the internet related to the Sega Master System and other 8-bit sega consoles. Actually updated, unlike this site.
SMS Tributes / Actively updated Sega Master System fan site
MegaDriver Sega-inspired band! You know you need your outrun. Check this out for all sorts of info about outrun and other Sega stuff.
Digital Press Online version of the magazine "Digital Press"- very cool site. Great columns, and more! Be sure to order a subscription while you're there!
The Phantasy Star Pages Let me say this- this page absolutely rocks. Everything you wanted to know, or didn't want to know about the Phantasy Star series is here.
UK SMS Page Ok, this page kicks butt. He's got a great amount of Techie info, which not many others have. I'd be tempted to steal it, but I won't..