The Security Committee of the Antiquarian Booksellers' Association of American (ABAA) has launched
Missing and Stolen Books Blog, to document, well, missing and stolen books. Committee chair John Waite writes: "The Security Committee invites all interested parties - booksellers, librarians, collectors, & others - to make use of this service, both as posters and to keep current about stolen and missing materials that are reported to us from around the nation."
I've added a link to the sidebar.