I have quite some books (despite my not so old age). I guess if I keep collecting them at this pace I will need a bigger house soon to store them, or I might have to give up some more space in the living room. In the past I have tried some computer programs to catalog all the books I have, but I never found any that I found easy to work with.
But last week I read in the newspaper about a site called LibraryThing. As a test I entered about two shelves of my books and I think I like the site. It makes use of different online databases, so that makes finding the books based on for example the ISBN number quite easily. And you can also see how many other people on the site have the same book and the reviews they entered for it.
And they also have a cool widget that you can use to show your collection on your blog for example. So below you can see part of the books I already entered. So if you are looking for a way to catalog your books as well, check out this site.