Here is a list of social bookmarking sites blogmarketingtactics.com/social-bookmarking/social-bookmarking-top-links.html
sometimes people will post just about all of them, I recommend trying out DP's search, I have alot of them boomarked, probably not all of them since new ones pop up everyday
http://pro-designs.blogspot.com/2008/01/building-your-page-rank-with-122-social.html This is a handy list.