I have a cheap ($15)version of the B&D workmate that Iclamp a homemade top on that I use for a shooting table. It works real well with a folding metal chair. I made a front rest out of some scrap lumber and have a rear sandbag rest from WalMart. Most of it I made up from scraps I had laying around the garage so I don't think I've got more than $25 in it, and the workmate does double duty as a work table/clamp when I'm not using it for a shooting rest. The whole thing folds down and the top comes off easily so I can put it into a car trunk or where ever I need to store it.

Here are some links to some pictures of it.

http://i23.photobucket.com/albums/b365/dmurphy317/Target%20Bench/DSC00147.jpg
http://i23.photobucket.com/albums/b365/dmurphy317/Target%20Bench/DSC00146.jpg
http://i23.photobucket.com/albums/b365/dmurphy317/Target%20Bench/DSC00145.jpg
http://i23.photobucket.com/albums/b365/dmurphy317/Target%20Bench/DSC00144.jpg
http://i23.photobucket.com/albums/b365/dmurphy317/Target%20Bench/DSC00143.jpg