I saw one of these in use, drilling holes in steel beams.
Just the thing for drilling holes in steel when you can't put the work
in a drill press. There's a large electromagnet that clamps the drill
on to the work. Terribly expensive, but I guess I could make or buy a
cheaper version using screw clamps

http://i7.tinypic.com/6763lew.jpg

Apparently it's a bit dangerous if the power fails while it's
drilling, because the magnet unclamps while the drill is still turning.