But if you would like to experiment with computer architectures, you can get something like the Altera DE-2 [1] and play around with really crazy sauce kinds of things, n-way associative cache with CAM register banks and dynamic register renaming? No problemo! And you do it all without soldering or wire-wrapping or anything. I have some PDP-8's and I love them dearly, but it is soo much easier doing stuff on an Arduino than a PDP-8/e.
[1] http://www.altera.com/education/univ/materials/boards/de2/un...