
HDR, or "High Dynamic Range" is a type of photography that utilizes several images in order to create one image that captures as much lighting detail as possible. I have a tutorial up here that explains how to do this in Photoshop CS4. There are more popular programs out there, such as Photomatix, though I tend to not be fond of the output of such programs, as they often come off as being extremely unrealistic.
I'm testing out a new HDR algorithm; in the past, I'd never really found an HDR program that could render realistic output in storm situation or handle the fact that clouds tended to move between shots. I think this one is zeroing in.
This photo was taken on April 23, 2006, in central Kansas. In the foreground are storm chasers Amos Magliocco and Robert Hall.
Below is a screenshot of the individual RAW files used to assemble this image:

Interestingly enough, it's kinda amazing how quickly light changes at sunset and how dramatic a difference this can have on storm appearance. For example, the non-HDR image below (which I like more) was taken not long after the HDR image above, but it is completely different:



