Here's a few sites. Not sure which one qualifies as the best:- http://www.stuckdomains.com/ http://www.domainannounce.com/ http://www.justdropped.com/ http://www.unwanted-domain-names.co.uk/ http://www.digestdomains.com/domains/dropped/ http://die4domains.com/ http://www.domainleft.com/
This site is crap. They list all forged domains. You might be shocked when seeing the title "Some PR 8 Dropped Domains that will be available for registration on 8th April 2009"
I have another option for you and its FRRRREEEEE! plus no membership required. Its worth a look at least. The site is very much work in progress but there are at least 40 Just Dropped category lists of domain names posted each day at the moment in the Just Dropped section. The .COm Graveyard section is also live. The Expiring Soon section will be live again soon and I am working on the Live Domain Stats tool that will allow you to get the CORRECT stats for each domain listed. Let me know if its any good and PM me with any suggestions about things you would like to see included on the site. The site is http://www.dndizzy.com
The PR of dropped domain are generally forged one or in case if it is genuine the PR start dropping once the domain is deleted or dropped. So be careful buying dropped domain name for the sake of PR.