To use DemoHelper, just right-click its System Tray icon and choose Draw. Now your mouse cursor works like a magic marker: click and hold the left button to draw freeform lines. Click and hold the right button for arrow lines. If you prefer a highlighter, tap M on the keyboard.
When you're done drawing, highlighting, etc., a simple press of the Esc key erases your work and restores your mouse. (See the product page for a full list of features and their corresponding mouse/keyboard shortcuts.)
DemoHelper also has a Zoom mode, which could also come in handy for spotlighting a specific area of the screen. The zoom level is controlled by your mouse wheel or the up/down arrow keys, while the mouse itself pans around the screen.
This is one terrific little program! If you give a lot of presentations, product demos, tutorials, and the like, you'll definitely want to add DemoHelper to your toolset. [via gHacks]