lcsh.info is a project that has been discussed in the recent past on NGC4LIB. For a brief explanation that begins
This is an experimental service that makes the Library of Congress Subject Headings available as linked-data using the SKOS vocabulary. The goal of lcsh.info is to encourage experimentation and use of LCSH on the web with the hopes of informing a similar effort at the Library of Congress to make a continually updated version available.
as well as acess to the dataset, go here.
Bernhard Eversberg has used the dataset created by lcsh.info to help users of the database at Universitätsbibliothek Braunschweig search by authorized heading when they only know the keyword, by starting their search here.