Humans can't see into the infrared, but this camera can. It can take pictures in complete darkness, and also be used to explore how totally bizarre the world looks in the infrared spectrum.
The Midnight Shot NV-1 Night Vision Camera is perfectly happy to function as a simple point-and-shoot digicam, with a five megapixel sensor and VGA video. The reason you might want this camera over any other, though, is that its sensor is also sensitive in the infrared, and with a flick of a switch, you can change it over to night vision mode. Or it might be more accurate to call it "pitch-black vision mode," since with the aid of an IR illuminator, the camera can take pictures even when there's no light at all.
That's pretty neat, but you can use the IR sensor to take daylight pictures too, and it'll show you what the world looks like in a way that your unaided eyes can't. In the infrared, plants show up very strongly but the sky doesn't, giving you images where trees look like ghosts and the sky looks black. Using different filters can provide even weirder effects.
To get this to work, you'll need to add your own filter to block out visible light, but it's cheap and easy to make one with stuff you probably have lying around the house. The camera itself is $130 from ThinkGeek.
Check out the gallery for some mind-bending examples of infrared photography.