Yet another unfamous but very nice documentary. The Red Stuff tells the story of Soviet Space Program. This is very unique and valuable since all documents on this subject deal with Sputnik,Soyuz and Gagarin. This documentary tells the story of other cosmonauts with nice soviet archieve footage and interviews with people who REALLY went to space.
See DVD info on amazon.com or on IMDB.
There is another documentary on Soviet Space Program named "Red Star in Orbit" which I mentioned here.