LibraryThing is an online site which allows you to catalogue your books, keep track of your reading, write book reviews, search for people with similar libraries, get reading recommendations, and apparently do a whole host of other things. One thing I like is the Groups page, where I discovered a group called "Livejournalers" (376 members), and another called "Librarians who LibraryThing" (1488 members).
You can catalogue up to 200 books for free; to catalogue more, it's $10 per year or $25 for life. Since I could use up over half of my free allowance just on my cookbook collection, I'll definitely be taking the $25-for-life option.
So, people, if you look around at your books and feel like you're the lion tamer at the circus with a whip and chair trying to hold back and maintain control over a group of hungry lions, then maybe LibraryThing is for you. Go check it out at least, and if you like it, spread the word. And maybe I'll see some of you there in the Livejournalers group once I join. :-)
Note to lark_about: Wow! Had you heard of this before? They're based in Maine, apparently, and have gotten a lot of mainstream media coverage (some of the references and links are up on the home page). Everything from The Wall Street Journal Online and The Guardian to PC World, USA Today, and Public Libraries magazine.