Some great documentaries that come to mind are:
 
   If You Love This Planet   - National Film Board of Canada
                               (If you are in the U.S., I'm not
                               sure if this is available, since
                               it was declared anti-American
                               propaganda by the U.S. Justice
                               Dept.... which didn't stop it
                               from winning an Oscar.)
   Best Boy                  - Also won an Oscar, aired on PBS
   Swimming to Cambodia      - Aired on PBS
   Titicut Follies           - Copies are owned by various
     (or anything else         educational institutions,
      by Wiseman)              Frederick Wiseman doesn't allow
                               any of his work on video.
   Cryogenics                - Aired on PBS' P.O.V. series
   A Rustling of Leaves: Inside the Philippine revolution
   Letter to the Next Generation  - Aired on P.B.S.
   Rape Stories              - Available on video (Women Make Movies?)
   Mile Zero: The Sage Tour  - National Film Board of Canada
   Not a Love Story: A Film About Pornography - N.F.B.
   Navajo Talking Pictures   - dir. Arlene Bowman, not sure where
                               distributed
   The Last Train Across Canada - Aired on P.B.S.
 
I hope this list is helpful... If you'd like any more details about
these films, let me know.
 
Kathy Presner, Montreal