Actually, there are quite a few rings out there. The Ring of Green was recently resurrected by the very people here at The Technodrome.
http://www.thetechnodrome.com/webrings.shtml
And you can always search Webring:
http://dir.webring.com/rw
Or follow the rings on other people's sites!
Reminds me, I gotta get around to joining a few rings.