The official website of Leonard Bernstein includes… well everything. Very comprehensive. Includes a biography and a series of “time line” events.
http://www.leonardbernstein.com/

The Library of Congress Leonard Bernstein Collection
“This online Leonard Bernstein Collection makes available a selection of 85 photographs, 177 scripts from the Young People’s Concerts, 74 scripts from the Thursday Evening Previews, and over 1,100 pieces of correspondence, in addition to the collection’s complete Finding Aid.” http://memory.loc.gov/ammem/lbhtml/