I hear the question asked all the time. And I know from my own experience that there is no simple answer to the question, "How do you buy expired domains with PR value?"
For years now, domaineers have kept this information close to the vest, as heavily guarded information, because they could buy expired domains and flip them for a quick profit. While I don't consider myself to be a domaineer, I am in the business of buying domains that have PR value, developing useful, unique content on them, marketing them, and then either reselling them, or selling advertising on them. So, I don't particularly want more competition (and believe me, there's tons of it).
That being said, I don't see many people doing the amount of research I do on domains that I do, and I'm usually willing to pay a premium on domains I really want, so i don't expect that providing some basic information here is going to hurt me much.
The first thing to understand is that domains with good pr value never expire. Nearly all registrars nowdays will auction domains off before they actually expire, and it has become a profitable business. The expiring domains are purchased by people specifically watching for expiring domains who know where to buy them.
You also need to know that that days of picking up a valid pr5 expiring domain for less than a few hundred dollars is long gone.
not only will the domain cost you money, but it's probably also going to cost you money in the form of a 'membership' to a place where you can buy these expiring domains. Not to mention there's the registration fee involved.
There's basically three different things you get for the 'membership fees'.
1. The opportunity to bid on domains that may expire in the next 14 days. There are a few different places you can go to get domains like this, such as www.tdnam.com and www.snapnames.com Unfortunately, they don't provide much in the way of domain statistics. They don't give you the pr, traffic, or any other stats, you have to research it yourself.
In order to do this, they will usually give you a list you can download with thousands of domains in it that will be up for auction. Probably about 97% of these domains will have pr0.
Also, there's not very many tools out there that help you check pr value of domains in bulk. The best I've ever found is at www.digixmas.com , and even that doesn't get all the way through a full list of domains. Try to check the pr on a few thousand domains a couple of times in the same day, and you're likely to get your ip banned from Google.
finally, keep in mind that if you do win the auction, these domains are not expired yet, and the original owner may still renew for like a week after the auction.
2. Access to dropped domains that a domain broker has purchased with intent to resell. These guys go to the actual live domain auctions and buy expiring domains in bulk, then sell membership to people, to give them the opportunity to bid on domains. In my experience, membership is a little more expensive, and you still have to pay about the same amount for the domain. And, you still don't have statistics provided on the domains, like pr or alexa rank. You have to do all the research yourself .
3. The opportunity to attend live domain auctions, such as at www.pool.com. This is probably the cheapest way to buy a good domain with pr, but you'd have to be in the market to buy in bulk for it to be worth traveling to a live auction. You can bid by proxy, but I find the rules for this a little confusing, and complex. And again, pr and alexa is not provided. They give you a list of thousands of domains beforehand, and you research them yourself. Out of 1000 domains, there might only be 100 with pr value.
4. Aggregated analysis of domains from the aforementioned services. These guys take all of the domains from all of the aforementioned services, and check various stats, like pr, traffic, Alexa rating, etc., and you pay to see it. Then you can go to the source and purchase it yourself. My favorite in this class is at www.freshdrop.com
If you have other methods, please feel free to list them in the comments below.

