There are services like domcop.com, however it is not free to use. They offer you free trial if I remeber correctly, pretty good categories you can search within, however it was too expensive for me.
Expired domains has the best search tools and that makes them popular. I sometimes use freshdrop.com, but its a pay service. I use it because I cans tore my search criteria which is based around 50 keywords. That way I don't have to enter it each day.
If you're looking for a free service to search for expired PR domains then ExpiredDomains.net is going to be your best bet.. Go signup real quick and do some browsing, it's free and easy! lol