LibraryThing’s thingTitle
From Introducing the thingTitle API, from LibraryThing’s Thing-ology blog:
Announcing another simple LibraryThing API. Feed it a title and it will return all the ISBNs from the most likely LibraryThing “work,” the LibraryThing title and a link to the LibraryThing work page.
It’s simple to use. If you look at http://www.librarything.com/api/thingTitle/The%20Three%20Musketeers (notice title in URL) you’ll get some XML back including the URL of the work LibraryThing thinks it is and a list of ISBNs of manifestations it thinks go with the work.