Ehh...I'm all for assembling one's own PC (cheaper and better than buying a pre-built, every time!) But it's hardly the same thing as working with the old machines, in my opinion - even on user-assembled PCs you're still usually running an OS that puts you layers and layers away from the hardware and doesn't even come with a programming language...
Awww...c'mon now! There's bash scripting, python, java, haskell

Of course, it isn't quite assembler and basic, but then python and haskell are pretty fun and not terribly complicated.