In the Library of Congress Classification System is being touted on O'Reilly's XML.com as a useful tool for organising your books collection.
The great thing about it is that it uses letters of the alphabet to break down all human knowledge into top level classifications. And TWO of those - E and F - are for History:America. D is for History (general) and history of Europe. Military Science and Naval Science get their own letters, too.
And they say that classification systems are influenced by the culural assumptions of the classificatee. Who knew?
Please, point your browsers and laugh at:
XML.com: The Library of Congress Comes Home