Social Bookmarking has being an effective Strategy For Seo since years.If you do social bookmarking on 1000 sites but with no pr or broken links that won't help your website's rankings much and that also might effect negatively to your site. But if you do social bookmarking with high pr and on good reputed sites than only 10 links will boost your rankings. Here is a list of high pr social bookmarking sites with their pr. #1 http://digg.com/ pr-8 #2 http://www.reddit.com/ pr-8 #3 http://delicious.com/ pr-8 #4 http://slashdot.org/ pr-8 #5 http://www.fark.com/ pr-7 #6 http://www.diigo.com/ pr-7 #7 http://www.dzone.com pr-6 #8 http://identi.ca/ pr-8 #9 http://www.connotea.org/ pr-8 #10 http://blinklist.com/ pr-8 #11 http://www.folkd.com/ pr-7 #12 http://www.citeulike.org/ pr-8 #13 http://www.mister-wong.com/ pr-7 #14 http://www.dzone.com pr-6 #15 http://www.linkagogo.com/ pr-6 #16 http://www.bibsonomy.org/ pr-7 These are the must do social Bookmarking sites. If you do social bookmarking on these sites. It will Boost You Rankings. I will share more useful new high pr sites which arrive . All the best for your Bookmarking.