If you can cut, fit and weld mild steel, a machine stand is easy. I like
to make the legs out of 2x2x¼" or 2x2½x¼" angle, and I like ½" plate steel
for the top. I like to cut/drill plates to match the caster plates, and
weld them on and paint (or get galvanized) the whole stand, then bolt on
the casters. If you like you can put drawers in. If you do put drawers in,
make them very sturdy, and make them deeper (top to bottom) than you'd
think. I made a lathe stand this exact way and it is very rigid and stout.
Plans are at http://www.tinyisland.com/images/stand.pdf in the dreaded PDF
format. I also made a surface plate stand which was similar, see the pic:
http://www.tinyisland.com/images/splate2.jpg (this is my old shop).

It isn't completely trivial to fit everything so it's nice and square
after welding, but it is easy to build a very rigid and stout stand you
can feel real good about for as long as you own it.

Grant Erwin
Kirkland, Washington