Here's a list of bookmarking sites consolidated from some of the above links. I've also run them through SB and grabbed the homepage PR where possible. Hope it helps.
Url PR
www.twitter.com 9
www.citeulike.org 8
www.connotea.org 8
www.del.icio.us 8
www.digg.com 8
www.fark.com 8...