If you use Social Bookmarking sites in any kind of promotional fashion, you may be interested in seeing a list of 100Social Bookmarking sites with their google pagerank, as of Jan 2008. I plan to do an updated version of this myself soon, sign up to my feed to make sure you don’t miss it!
http://www.squidoo.com/100-social-bookmarking-sites-with-google-pagerank