The World Digital Library (WDL) is set to go live (officially) tomorrow morning, April 21st. However, the site appears to already be live (Monday, April 20th) at: http://www.wdl.org.
From a Post by UNESCO:
UNESCO and 32 partner institutions [including the Library of Congress] will launch the World Digital Library, a web site that features unique cultural materials from libraries and archives from around the world, at UNESCO Headquarters on 21 April. The site will include manuscripts, maps, rare books, films, sound recordings, and prints and photographs. It will provide unrestricted public access, free of charge, to this material.
For more information, go to ResourceShelf » World Digital Library Set to Officially Launch Tomorrow, Get a Head Start Today.