Two unrelated links, at opposite ends of computing's temporal spectrum:

From tiddly-pom comes a site about one of the first computers, the EDSAC. A simulator is provided, with instructions, and programs to run (including Conway's Game of Life). It's hard to imagine using a computer this primitive, but imagine how jazzed they must have been that the thing worked at all, and it was a great leap ahead of what came before it (paper and pencil, mostly).

Indirectly from Dan Bricklin comes Open Croquet, a wild-assed experiment about a potential user interface, with 3D navigation among programs and computers. The whole thing is built in Squeak, a dialect of Smalltalk, and has a number of software luminaries working on it (David A. Smith, Andreas Raab, David Reed, and Alan Kay). It's easy to say "it'll never make it onto everyone's desktop", but who knows? I'm sure people said that about other things Alan Kay has come up with, like windowed GUIs.