There was an old Poser database created by Katrina, but it never really got updated and is very out of date. It still has some useful information though, and you can find it here.
New Poser Video Database
We're in the process of putting together a new Poser database specifically for videos, which you can find at p/hlp/materials/PoserVidsOnSlate.xls. Most videos have not been added yet, so your best bet is emailing Cassandra Donatelli, and asking her whether such-and-such a video exists.