The Missing and Stolen Maps Database, supported by the International Antiquarian Mapsellers Association (IAMA) is now live. First announced back in February, the database was designed by a large group of librarians, map collectors, dealers, and others. It is "free of charge, fully searchable, international in scope, and accessible using individual usernames and passwords." Registration is required to post information about a missing map, but not to search or browse the database.
I strongly urge librarians at institutions where maps have been reported missing to add information about them to this database. It can only function successfully if it is populated, and I think I join all those involved with its creation in hoping that it realize its potential.
I've added a link to the sidebar.