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.
NB: ZoomIt also includes a fullscreen countdown timer.
Simple and and powerful utility for screencasts, webinars and presentations. If you do live demo from your screen to public give it a try!
Microsoft uses this software.