This month Unesco launched World Digital Library (WDL), which makes available on the Internet, free of charge and in multilingual format, significant primary materials from countries and cultures around the world.
The web site boasts that every UN member country is represented by content on WDL. Metadata is provided in seven languages. The WDL "focuses on significant primary materials, including manuscripts, maps, rare books, recordings, films, prints, photographs, architectural drawings, and other types of primary sources. One of the WDL's content objectives will be to work closely with UNESCO's Memory of the World program to make publicly accessible digital versions of these collections."
Browsing is available by place, time, topic, material type and contributing institution. Where appropriate links are provided to the url of the original resource.
The site is hosted by the Library of Congress. Content comes from the World Digital Library's partners, "mainly libraries, archives, or other institutions that have collections of cultural content that they contribute to the WDL." The idea of a digital library was first proposed by James Billington, then Librarian of Congress, in June 2005. Not surprisingly at this point the largest contribution (505 items) is from LC.
Addendum: BiblioOdyssey has a typically rich blog post illustrating the depth of visual treasures currently covered by WDL. Definitely worth a look.