There's work that Feynman did on the Manhattan Project that is still classified. I believe it was an unpublished formula to determine the yield of the atom bombs.

Some videos of Danny Hillis talking about Richard Feynman and Thinking Machines:

https://www.youtube.com/results?search_query=danny+hillis+ri...

Also listed this:

https://www.youtube.com/watch?v=cNaEI70hT-o

Danny Hillis article on Feynman (if you prefer reading):

https://longnow.org/essays/richard-feynman-and-connection-ma...

Feynman computer science videos:

https://www.youtube.com/results?search_query=richard+feynman...