I saw this tool at a recent MSDN presentation. The inking works well with a tablet and allows you to draw on the screen on the current application and then once disabled, it goes back to normal program functions. The zoom is nice too when projecting to a larger screen.
ZoomIt is screen zoom and annotation tool for technical presentations that include application demonstrations. ZoomIt runs unobtrusively in the tray and activates with customizable hotkeys to zoom in on an area of the screen, move around while zoomed, and draw on the zoomed image. I wrote ZoomIt to fit my specific needs and use it in all my presentations.