I've gotten good targeted quality traffic from MyBlogLog. But I find you need to force the action. I go and visit members that have my keyword tags, visit their MyBlogLog profile, leave a message... visit their blog, and leave a comment.
Did you know you can add links to anything here? So you can help others out and link to MyBlogLog. (If you think about it for a minute you could even link to your own MyBlogBlog community and build your group, for example.)
I get good traffic from articles I submit on www.scribd.com Some of my sites get a good response from reddit and some from digg. The traffic seems to come from different bookmarking sites depending on the blog content
MyBlogLog has been working pretty well for me. Just joined BlogCatalog, but my first impressions are that the quality of the traffic is better from MyBlogLog.
PlugIM and MarkTD (internet marketers), Digg yes! Reddit, Shoutwire, Plime. Also sites like Stumpleupon, Newsvine and Only Wire. I posted these earlier but needed to take out a link.
Mine is definitely BlogCatalog. I find it to be a much 'warmer' place than MyBlogLog. The crowd is definitely more friendly and helpful and will Stumble your posts without being asked or prompted to. At least, that has been my experience.