At Macworld Expo last month, Peachpit Press included a presentation area as part of their booth. In addition to letting authors like me demonstrate techniques found in our books, the area was used by Apple and the National Association of Photoshop Professionals for hands-on training sessions. It sported a Power Mac G5 hooked up to a fairly large projector that showed the Mac's screen large enough for people to see.
The problem with setups like this is that it's sometimes difficult to follow the mouse pointer as the presenter performs actions. In this case, it was often easier for me to take a step to the left and point out some iMovie interface elements using my hands, but of course then I wasn't using the computer, so nothing was happening on screen. The problem is exacerbated on much larger screens, especially when demonstrating applications (such as Final Cut Pro or Adobe Photoshop) that have a plethora of windows, palettes, and other interface elements. In the past, presenters would often move the mouse pointer in circles to highlight an element - leading, at least in my case, to tired eyeballs trying to track the swirling cursor.
PinPoint -- This year, however, the folks who set up the presentation Mac added a tiny detail that made it twice as easy to follow along: a small red circle surrounding the mouse pointer at all times, courtesy of MacChampion's PinPoint 2.1. This little Mac OS X utility lets you change the size, color, transparency, and shape of the cursor highlight; in addition to the seven built-in shapes, you can download others such as arrows or even Halloween images from the company's Web site. You can set it to always display, or show up after a set amount of time to locate it easily when you step away from your computer. PinPoint 2.1 costs $10 normally, but is available for free to visually impaired persons (though the free version cannot import new highlight shapes); it's a 1.7 MB download.
Mouseposé -- If you don't need to give presentations, but get frustrated when your mouse pointer disappears (darn those dual 30-inch Apple Cinema Displays!), another simple utility that can help is Boinx Software's Mouseposé (that's "mouse-po-zay" with an accented E at the end). When you hit a function key, this application dims the screen except for a circular area around the mouse pointer. You can change the size of the circle, as well as the opacity and color used to mask the rest of the screen. The effect stays on for a certain amount of time, or until you manually turn it off.
One disadvantage of Mouseposé is that you can only choose a function key as a trigger, which makes it a little more awkward on laptops or for people who launch applications using their F-keys. It's also not as useful for presentations when you need to see the screen as a whole (though setting the opacity at its lowest setting is still functional, even if the screen is slightly darker overall). Still, Mouseposé is simple, effective, and is a free 255K download; it requires Mac OS X 10.3 or higher.