There is a relatively new resource on the Web named Blocked PR List, which gathers information on which popular sites do not funnel PageRank to external sites.
Back in January, digitalpoint posted a entry here named Google Blocking Domains From Passing Page Rank?. This entry discusses a PR10 site's, phpbb.com, inability to pass its PR10 to the pages it links to. Too bad for those that purchased text ads on the site for the sole purpose of increasing PageRank on an external page.
Blocked PR List is a simple Web page that lists out these types of sites. The owner told me:
We fully expect that Google will penalize both the BlockedPR.com and Textlinkbrokers.com site. We get emails fairly often from people telling us how we're going to get banned for putting up such information. I think its interesting how alot of people assume that we did not think of that possibility. I would however like to assure everyone that we take every possible precaution to insure the safety of both our link clients and link partners. We have learned from mistakes of the past and mistakes of others and beleive that we have the safest linking network out there.
Currently the site is up and running. The list of sites is still short, I would guess, when the list grows so will its interest.