So, I found out about LibraryThing, which lets you catalog your books on-line. I decided this would be handy for lending out books to my friends - they can look at what I've got, rather than it depending on my thinking to suggest something.
Free membership on the site lets you catalog 200 books. This sounds like a lot, until you start actually entering them. It's enough to sound good, but anybody who's likely to want to use the site is going to hit the limit.
My library, if you ignore technical books, bridge books, RPG books, and bad game fiction from the late 80s-early 90s, isn't actually that large, so I figured I'd squeak in under the wire, then decide if I want to pay them money later.
Turns out that the books in my initial cataloging spree number two hundred... and three.
For now, I'll hack out a few books, probably some of the bridge books that made it in, but now I'll probably be giving them money sooner rather than later.