In 1943 the chairman of IBM claimed that there was only a market for 5 computers in the world. Ken Olson repeated his mistake in 1977 and claimed that there was no reason for anyone to want a computer in their home.
Backstory Radio presents an interesting radio show called “The Future Then” , which chronicles past visions of the future that never became reality. They have interviewed Matt Novak from Gizmodo’s Paleofuture blog.
Novak is also featured here: “You Are Not So Smart The Future – James Burke and Matt Novak” (1 hour)
Watch the Skies! is an old documentary on 1950s scifi.
In 1956 NBC’s Biography in Sound made this hour long tribute to scifi.
All Things Victorian presents an episode on steam punk
Watch Things to Come (1936), a prophetic film based on the work of H.G. Wells, one of the founders of scifi.
Finally, you should have a look at Future by Design, a feature length documentary on Jacque Fresco.