A question I'm often asked is how do I control presentations, i.e. how do I advance slides in PowerPoint, without having to sit at the computer.
You can, of course, use a wireless keyboard and/or mouse, but I usually use a Targus Wireless Presenter. It seems that the model I have (AMP02CA) has been discontinued, but the new one has most of the same functions. Other companies make similar products, but I haven't used them. I have used one with a voice recorder, but the audio quality is terrible.
A number of people like the Microsoft Presenter Mouse, but it is a little more expensive and requires a bluetooth receiver.
Most data projectors also come with "Page Up" and "Page Down" buttons, all you have to do is connect a USB cable between the projector and the computer. This does require you to point the remote at the projector, but if it's in the ceiling that shouldn't be a problem.
Another option is to use a tablet, either wired or wireless, which I'll write more about in a future post.
If you want to get creative, you can use a Wii Remote, iPhone/iPod Touch, PDA, or a mobile phone headset. I'll have to try the Wiimote one.