I first saw Silent Running shortly after it was made, while I was in college. It had quite an impact on me. The film has a strong environmental thesis, with two songs sung by Joan Baez. (I was an active and vocal member of Friends of the Earth and Zero Population Growth at the time.)
I still think it's a good science fiction film. Of course the three maintenance robots, Huey, Louie and Dewy (played by double-amputees inside the robot bodies, using their arms to move the robot legs) are the real stars. The set, which made use of the soon-to-be-scrapped aircraft carrier Valley Forge, is awesome. The special
effects are great for their day, too.