HDR (High Dynamic Range) photography is a technique that allows photographers to extend the limited dynamic range of digital sensors by combining several images taken with different exposures. Although it has a reputation for producing overly saturated, almost psychedelic images, when done properly it can reproduce the full range of colour and contrast that your eyes can see. Below is a good example of HDR done right, bringing out the contrast and colour in areas that were not exposed properly in the non-HDR shot.
HDR and Beyond is a good primer on HDR photography. To try it out, you’ll need a digital camera capable of bracketing exposures (preferably automatically) and shooting in RAW format and some software to combine the images.
I haven’t had time to play around with this yet, but I’m hoping to this spring.