No they're not worth it. It's like a banner exchange...nobody uses them anymore and they simply don't work. I'd suggest not doing it...it won't help any with SEO let alone with traffic. -.-
The only webrings I have used are at webring.com if you can find a webring with a small amount of highly trafficed sites it can benefit you. I wouldn't sugest joining a webring with thousands of sites but if your site is a very specific niche and every visitor is going to count then webrings can work.
The value that can be taken from a webring consists of only some occasional traffic. There is no PageRank value to be taken from it. All links from it run through a Redirect link on the webring server. I belong to only one webring, and I get about 50 visitors a month from it. It is not worth much in the grand scheme of things. Bill Platt
Webrings are not helpful because google doesn't like them. You might be getting 100 visitors a month thru them but just for that 100 you cant sacrifice the 1000 that google will send you. (I used webrings once, my websites have been better after removing them)
I actually still get hits from banner exchanges lol...not recommended though. You should consider the DP Co-op.
I used to run a successful computer hacking webring as funny as that was, and everybody in it had traffic from it. Get a solid topic and get to work on promoting the webring of your own and get websites linked up... then from there you'll have backlinks and [if "presented" properly] more traffic to your webring in general. And to you naysayers, here's why it works: Think back before other search engines were prominent, webrings existed because they received traffic just like: newsletters get read - articles get read and exchanged [sometimes] - mailing lists and forums get traffic - it's a similar concept of passing links around - hence the "ring"... so it is at work right now.