Michel, Whew, there are LOADS of possibilities and I am sure others on the
list will offer many. Here are a few general directions that the others
may not have immediately thought of:

World's Fairs and Expositions. Materials from these are rather easy to
come by (I found a COMPLETE -- weighing about 70lb -- catalog of the
Columbian Expo, at a flea market).   I'd sugget the two New York World's
Fairs from 1936 and 1964. These were packed full of such prototypes, some
even became reality and there were loads of fake props too or those ideas
still struggling (I remember at the 1964 expo, being able to make a
picture phone call to Disneyland -- to this day no one wants to BUY such a
product!!!). I also remember at the 1964 fair demos of Lasers and computer
translation. I now believe that IBM had faked the later, a live realtime
demo of perfect translation from Russian to English. Hey we STILL don't
have this perfected but you'd never know it from their 1964 demo!  My
favorite, the underground home of the future "FREE ADMISSION" (you just
had to pay to LEAVE).

Another avenue that might not immediately come to mind is from the world
of film. Besides the many films dealing with predictions of the future,
from "Flight to the Moon" to "Sleeper", some went to extraordinary lengths
of research and have nice documentation. A case in point was the film
"2001". In the year of its release "Industrial Design" Magazine did a
wonderful article on the product research and development that went into
the film. Every prop used was researched and then manufactured by the
actual industry. For instance, The Parker Pen company developed two
prototypes for the film. The floating pen at the beginning was an atomic
pen, designed to burn images into paper, an excellent foil for forgers --
of course Parker couldn't figure out just how to fit a reactor into the
pen but that's another matter! Parker also developed a prototype pen with
which you could "dial in" the handwriting style. Westinghouse designed the
food preparation units, Bell the telephones, and Honeywell, the controls
on the space suit sleeves. The suits themselves had to work since the
filming temp would place the air inside the suits well beyond 100 degrees
F, so they were air conditioned like the real things.

Of course one fun thing about future predictions is how far off the best
of them are. There were a flurry of articles a year or two ago about the
birth of the HAL computer at the Champaign Urbana campus. The moral I
guess is that if you are writing science fiction, never give an exact date
in the text!

I can't resist a bit of trivia. How did Orwell's novel "1984" get its
name?  Answer: It was written in 1948 and he just reversed the digits. But
then I must add that we should be thankful that the novel was not written
7 years later!

If my memory is correct, Verne or Wells (perhaps someone on the list can
help here) had an unpublished manuscript for a novel "Paris in the 20th
Century". Within the last five years the manuscript WAS indeed published
and is now available. The claims are that many of his predictions are
right on with a few whopper misses.

Last, my favorite avenues of research on the topic of future devices has
been the popular science magazines. Scientific American is full of such
devices. Also, many municipal libraries have patent abstract files. Often
the ideas of the future are developed years in advance but with certain
key ingredients missing the products just didn't work. Other times a
product is invented without anyone seeing the need. The perfect example
here is the Xerox process invented DECADES before anyone would agree to
manufacture it "What do we need this for when we have carbon paper?".

Richard Finkelstein
Boulder Colorado