I tried searching and couldn't find anything on this, but lately I've had some success using Google to hunt down WP MU blogs and create some backlinks. Search term: Code: inurl:"wp-signup.php" So for one of my Music niche's I did a search for that with +music attached. Found like 5-6 good networks with a PR3-6 on the main page. A lot of the networks will give you a ******** link to your blog if you have a lot of posts, or are new, etc. So for one blog I posted 5 posts/day for a week to get in the 'top 10 most updated blogs' on the network, which is a ******** link from a PR5 page to the blog using your blog name as the anchor text (which actually drove some good traffic too). A lot of people know about this already, but for those that don't hopefully it gave you some ideas.