Have looked online, but most of the time you are just directed to a page where someone is talking about dofollow social bookmarking sites. Got that one covered, actually want to know of social networking sites that are dofollow in the lines of Bebo, Classmates, Facebook, Flixster, Myspace etc. Also wondered if Ning sites are dofollow? As there are thousands of them around and link building with these would be pretty easy, cheers.
If you use the socialmarker.com free service, it gives you the option to only select DoFollow sites from the list.