I have been on a quest to catalog my books for ages. I had almost everything in a piece of software called Book Collector, which was decent. But that computer crashed and I lost it. I like the idea of everything being online so I can access if from anywhere. My current solution has been to set up MediaWiki on a private URL and use it's free form entry and category system to get everything in. But the drawback is it can't import information from Amazon or other sites.
There are a number of web based project though that do this. I am thinking of trying them all out and doing a comparison piece on them.
I currently have on my list:
librarything.com
goodreads.com
gurulib.com
allconsuming.net
listbook.net
reader2.com
shelfari.com
bookjetty.com
Any other sites I am missing?
Also, for my bibliophiliac friends, what are the things you want to do with a book catalog? (I want to make sure I am covering features other people use or want, but which I don't care about.)