HDR stands for High Dynamic Range and it is getting pretty popular. HDR typically involves merging multiple exposures into a single photograph in order to capture details that would be lost in the dark shadows or washed out highlights of a single exposure. HDR is great for shooting at night, where you typically have harsh man-made lights illuminating your scene. these lights tend to create very bright and very dark spots in a single photo. 

The easiest way to shoot HDR is to use bracketing on your camera. Even on an entry level DSLR, you can easily bracket your exposure in order to take 3 consecutive shots: one properly exposed, one under exposed, and one over exposed. You can use software like Photoshop or Photomatix to merge the images into a single, detailed and dynamic picture. I first learned HDR at stuckincustoms.com They have a great tutorial and even better content.

I have a habit of getting drunk when I edit my pictures. I tend to oversaturate and make photos a bit too "painterly", especially in HDR. If you can subtly use HDR to make a more dynamic, interesting image, it can be a really powerful tool.