There are two new list of out-of-print seforim available. The first, is via email, you can request the list from sba-at-sba2.com. The second is mainly a list of German imprints (it includes a couple of books Solomon Schechter owned) and can be viewed here. Additionally, Kestenbaum recently had their latest auction, unfortunately their catalog is no longer available online, but if you previously downloaded the catalog you can see the price results here.