You may not be aware of this, but most digital cameras can see infrared wavelengths that are invisible to the human eye. It's actually pretty easy to demonstrate this. If you've got a remote control nearby, such as the one for your TV, have a look at it. On the end that you normally point at the TV you'll see a dark plastic window, or possibly something that looks like an LED. If you press a button on the remote while looking into this end you probably won't see anything happening.
Now switch on your digital camera, point it at the end of your remote and look at it on the camera's LCD monitor. Now if you press any button on the remote, you should see the LED on the end light up, usually with a reddish glow. This is because the LED is actually an infrared emitter, and your camera's CCD is sensitive to infrared light. Note that this only works on digital cameras with a live monitor view. It doesn't work on most digital SLRs, because they have a built-in anti-IR filter.
The camera's sensor is only sensitive to what is called near-IR, which are infrared wavelengths that are quite close to visible light. This near-infrared sensitivity doesn't mean your camera is going to give you Predator-like night vision, but you can use it to take some highly unusual and strikingly beautiful photographs.