Online book collection managers

I've been thinking of trying to get my reading list transferred onto a
Web service. So far, the big 3 I know of are Reader2, Bibliophil, and
LibraryThing.

Anyone else on here use one of the above services or another service to
manage their book collections? Any thoughts on which service is best?
I'd also be interested to hear your experiences using such services.

Thanks for responding.