I have a new obsession and its called Blog Catalog! i joined ages ago but since then i have been drawn into the discussions section and i cant get out :)
It does actually generate quite a bit of traffic to your site and you can create a discussion about anything. My latest one is Jokes! Blog Catalog
It is actually a lot of fun and i have found a couple of new sites to join.
Last.fm for all you music fans: Last.fm
Squidoo for not sure who yet: Squidoo
Also i have set up a flickr page for those interested in my Photographs.