List of Dofollow High PR Social Bookmarking sites
http://www.techncom.net/2010/11/dofollow-social-bookmarking-site-list.html
850+ Free social Bookmarking site list with High PR
http://blog.sitesubmiturl.com/link-building/850-free-social-bookmarking-sites-lists/
700+ Dofollow social Bookmarking site list with High PR
http://blog.sitesubmiturl.com/free-seo-tools-and-markting-articles/top-social-bookmarking-sites-list-2010-2011-free-and-dofollow/
List of High PR Social Bookmarking sites
http://www.web2whizzing.com/248/social-bookmarking-list/
The list of high PR social bookmarking sites will help you a lot. Just start bookmarking from now and create backlinks for your site.