PointerStick is a tiny tool which adds a virtual pointer to your screen, perfect for highlighting specific areas during a presentation.
Just run the program and (by default) a very large pointer appears. Just move your mouse cursor as usual, and the pointer stick adjusts position to point at the same thing; anyone watching, even from a distance, will clearly get the message.
Of course a pointer stick of this size may get in the way sometimes, but fortunately this is easily fixed. Just triple-click the mouse, press Ctrl+Alt+Y or Ctrl+Alt+Z and you're able to toggle the stick on and off, which means it need only be displayed when you really need it.
If this still isn't quite good enough, though, clicking the program's system tray icon reveals a handy configuration console, where you can set the stick size, colour and style, transparency and more.
And perhaps most conveniently of all, PointerStick is portable, so this isn't something you have to install; just copy it to a folder sometimes and run it when necessary. (Don't worry about system resources, either. On our test system it typically consumed under 3MB when running on the background.)