California Institute of Technology
Benjamin Britten: Cal Tech Project Page
The focus of this project is Britten's War Requiem, but there are good photos, a bibliography, links and biographical information. The index page has information on many other Britten works.
Other
Music Web: Benjamin Britten (1913 1976)
Quite a bit of biographical information here at Music Web, a very complete listing of his compositions, and a good list of recordings as well.