"On December 9, 1968, Doug Engelbart and the group of 17 researchers working with him in the Augmentation Research Center at Stanford Research Institute in Menlo Park, CA, presented a 90-minute live public demonstration of the On Line System, NLS, they had been working on since 1962. The public presentation was a session in the of the Fall Joint Computer Conference held at the Convention Center in San Francisco, and it was attended by about 1,000 computer professionals. This was the public debut of the computer mouse. But the mouse was only one of many innovations demonstrated that day, including hypertext, object addressing and dynamic file linking, as well as shared-screen collaboration involving two persons at different sites communicating over a network with audio and video interface."
This demo became known as "The Mother of All Demos"!
Links:
sloan.stanford.edu 
(In Real Media format)
www.invisiblerevolution.net (In Quick Time format)
video.google.com (Google Video, flash player or avi download)
The demo also features in Doing With Images Makes Symbols.
And the man behind the camera? Stewart Brand, later of "Whole Earth Catalog" fame.
(The first issue of the Whole Earth Catalog was published just prior to this, in the fall of 1968, but they weren't famous until the Last Whole Earth Catalog in 1971.)
This demo resurfaced recently as a demonstration of "prior art" to challenge British Telecom's patent on hypertext links.
The video segments available on MouseSite for this demo are some of the most fascinating things I've seen in a long time. We're talking 1968-- almost 33 years ago-- people were using technologies that companies like Apple and Microsoft still can't get working right! I highly recommend that anyone who has a high speed connection to the Internet (these video files are encoded at 200k/bps) spend a bit of time and watch them. Aside from the obvious technologies referenced at the start of this page, you'll see tantalizing glimpses of the languages they used, and a hypertext programmer's environment that features outline views to show various levels of detail (like so called "folding editors").
The text on MouseSite states that 1000 computer professionals were there. I'd be interested to know some of the names in that audience. Any Wiki folk? I'd love someone to comment on the "vibe" of the demo, and if it generated much interest in the participants.
I've seen this demo. Of course it is amazing. However, saying that Apple/Microsoft/your-(least)-favorite-company "still can't get [it] working right" is asinine. Every programmer knows the difference between a demo and a product you can actually put in users' hands. It's especially easy for a demo to look coherent and blissful, because everything that the demo programmers work on can be refactored as needed for the one demo. The same is simply not true of software in the Real World. -- Arlie Davis
Which aspect of Engelbart's demo are you claiming is unrealistic to achieve in Real World software 37 years later??? -- Doug Merritt
That's a rather jaded point of view. Ever seen Rainer Joswig's demonstration of Symbolics LISP machines? (lispm.dyndns.org ) The models whose use he demonstrates were in full production, used, if you will, in the 'Real World'. Obviously, the astronomical growth in the abilities of hardware over the years has dramatically improved the modern computing environment, but the PC revolution lost something in terms of functionality of software (i.e., just-working and integration), whether you speak of Windows, Unix, or even Mac. We have much to learn from the LISP, Smalltalk, and NeXT machines of days goneby.
Engelbart's lab at SRI was already using the NLS system internally, so it was more than just a demo (but not a commercial product).
The part that projected the images up on the stage was more of a Rube Goldberg thing, because the computer was in Menlo Park and the auditorium was in San Francisco, and they had to build their own two-way data link between the two. The hero of that part was an engineer named Bill English (who later worked at Xerox Parc).
The whole history of Engelbart's research can be found in Boot Strapping by Thierry Bardini ISBN 0804738718 which includes photos of real people using the system at SRI "ca 1968".
See also Chapter 9 of Tools For Thought by Howard Rheingold ISBN 0262681153
See original on c2.com