I stumbled across two sites yesterday which do exactly what I have been looking for for a long time: they let you enter the books you own into a database. Don’t ask me why I want to do that, I just think it’s nice to have lists of everything. So there.
LibraryThing seems to lean a bit more toward the social software side, bibliophil on the other hand seems more robust. Another big difference is that LibraryThing is only free for the first 200 books. Afterwards you either pay 10$ per year, or 25$ per life. Considering that it’s still in Beta, I wouldn’t be willing to bet on them being here in 2 1/2 years.
I spent the better part of yesterday entering ISBN numbers into bibliophil.org, but since they let you export your database in an Excel CVS file, and since LibraryThing then lets you import that very file, I’ve now got my collection in both of the services. And right now there are only about 180 books in there, so I’ll still have some time left to decide on what service I’ll be using in the future.