I just released a Javascript/JSON API to LibraryThing core work data.

http://www.librarything.com/thingology/2008/03/first-cut-works-json-api.php

It's basically a riff on what Google did recently—a way to link to
LibraryThing if we have a book, and not if we don't. It also includes
copy and review counts, and the average rating. It takes ISBNs, LCCNs
and OCLC numbers.

Next up will be a JSON API into member books, so members can design
their own widgets and mash their library up with the contents of a
page.

It's all very beta, and my ears are wide open.

Tim

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Check out my library at http://www.librarything.com/profile/timspalding