For a little while now I've been publishing some lists of domains that are available to register, which have PageRank because they were previously registered but are now expired. A few people asked me how I was getting those lists, but I never really explained it, because it was quite a laborious process. Every day I would download a list of about 60,000 expired domains, parse the ones with the TLDs that I was interested in, chop them up and feed them into an automated PageRank validator, and then of the ones with PR, see which were still available, and which had real PR. Of all the domains that I went through, it was a very tiny percentage that are still available, and weren't simply parked domains or redirects.
Well, a new website has just been launched that makes it far easier to find expired domains. The site is called Expired Domain Up!, and it boasts of some great functionality. Basically, the database is updated every single day, listing domains that will be available the next day. You can filter on domains with specific PageRank, sort by TLD (such as .edu domains), look for domains with Yahoo and DMOZ backlinks, and see the number of indexed pages in major search engines. If you'd like one of the expired domains with PR, the system shows you where to buy or bid on it.
If this sounds interesting to you, right now is the time to sign up, because for the time being it's free. I'm not sure how much they'll charge in the future, but whatever the cost it can easily be recovered by buying an expired domain, building the site, and selling links, posts or the site itself!