Check this site for more info:-
1. http://www.socialcliff.com/sites/free-high-pr-dofollow-social-bookmarking-sites-list.php
2. http://www.tutorialwatch.in/seo-off-page/social-bookmarking-sites-list/
3. http://www.mybloggingplanet.com/2015/05/high-pr-do-follow-social-bookmarking-sites.html
4. http://www.sourcewp.com/free-dofollow-social-bookmarking-sites-list/
5. http://www.itechpassion.com/free-dofollow-social-bookmarking-sites-list-2015/
