My buddy built one with 2"x2" square tubing and a large piece of flat stock for the top (I think the top is about 3'x4'). It's on casters with threaded feet so you can move it and level it when in use. Added bars between the legs to hold all of the welding clamps. Painted the legs black and just keep the top treated to prevent rust.
His friend liked it so much, he paid him to build another. We got the materials at Alro and just put it together. Really wasn't too bad to do.