Some high PR sites for link building

http://www.guinnessworldrecords.com PR8
http://www.linkedin.com PR8
http://www.arenafootball.com PR7

http://www.linkedin.com PR6
http://www.residentadvisor.net PR6
http://www.dontstayin.com/members PR6 

You can search more for these types of links , and build back links for your sites