I saw someone a few months ago somewhere (link out of the maptools forum perhaps?) where a GM used Photoshop with a projector mounted above the gaming table to create a battlemap for real miniatures. He used various PS layers to show/hide features such as secret doors, etc as things were found and had a top layer overlay which acted as a sort of "fog of war/darkness" for unexplored areas which he erased as players entered line of site/vision range.
Question is, how many other people use their computer at the gaming table (for face to face) using a projector/second monitor/whatever to reveal map elements? Maptool, ViewingDale, etc would also be counted in this category