First machine/plans recommendation?

When I started woodworking, I read everything I could on table saws.
I fretted endlessly about getting the "wrong" tablesaw and wasting
$1000 or so on a lemon. It seems everyone had 45 different ideas of
what a "must have" feature for a saw would be.

Then I had a brilliant idea. I went out and bought a delta benchtop
saw (the "toy" ones for about $100) and learned the basics with it.
As I found faults, I searched for "fixes" on the net, in magazines,
and from watching "Nawm". At the end of three months, I knew exactly
what I "had" to have in a saw and purchased a Delta QT-10. Not the
most expensive (actually in the low budget range) but fits me to a
tee. No wasted money, no regrets.

I'd like to approach CNC in a similar fashion. One big difference is
that I want to build my machine, not buy pre-made. This first
machine doesn't need to be accurate to 0.0000000001 mm. It doesn't
need to be able to mill cobalt at 6m/second either :) It just needs
to be able to show me all the basic elements of CNC machining.
(Like, what the hell is a ballscrew!) I'd prefer not to have a
complete dog of course, but I'm "fault tolerant". If you've ever
used one of those plastic benchtop saws, you'll understand what I
mean! Small is better, the less money I have to put into the
learning machine, the better.

I'd like to hear from anyone that successfully built a small machine
from scratch. Preferrably ones that didn't have part sourcing
problems :D WHich plans did you get? Which controller? I don't care
if it was less than stellar, tell me anyway :D

Thanks!