So I had no idea that www.librarything.com would be so damn addicting! So, it's a site where you can build a library of the books you own, tag them, rate them, etc. Doesn't really sound that special, and I signed up thinking it would be tedious at best and I'd probably only catalogue a few of my books and then get bored. But no! The interface is fairly good (not too confusing, intuitive for the most part, lacka few nonessential features) and then once you have your books uploaded you get amazingly addicted to searching for other books, joining groups, finding out how obscure your collection is, and more! Agh, I've been on it for 2 hours already. And now I have so many more books I want to read!
In short: go join. It's awesome. Except now I really, really want to go to the library. Or buy stuff from Amazon. Or get books in some other way that would still lead to me not getting any work done ever.