Here is 25 high pr social networking sites where you can build backlink easily.
All Topics - The Latest News Headlines, Videos and Images - Digg
Technorati
World's Largest Professional Network | LinkedIn
Doctor.net - Health News - Drugs & Supplements - Health Living - Eating & Diet - Parenting & Pregnancy - Health Videos
9rules
http://www.blogoria.com/
Yahoo! Voices - voices.yahoo.com
http://www.propeller.com/
bloggingzoom.com: The Best Search Links on the Net
Current TV | Politics, News Analysis, Commentary and Opinion
kirtsy
Curated technology news.
bibsonomy.com - bibsonomy Resources and Information. This website is for sale!
Welcome to Flickr - Photo Sharing
Newest Links
NowPublic.com | The News is NowPublic
coRank > A better way to get, keep and share the web you want!
clip clip, do do, share share : clipclip
linkaGoGo - free Online Favorites manager and Social Bookmarking Application
Mister Wong | Social Bookmarking Tool
edopter - social trendcasting
Yahoo!
Welcome | Chime.in