I just discovered a great Photoshop (Both Photoshop and Photoshop Elements) tips blog called "Dear Debbie".
Debbie has a post that shows how to ad zap to images. I think this is of particular interest to real estate photographers. You want your images to have that zap that Debbie is talking about. So many images on real estate sites have a dull look. This technique gives images that crisp punch you need for an image to stand out.
Notice that the technique Debbie describes works only if you shoot RAW. It makes use of the fact making image adjustments in RAW conversion does not degrade the image. I think this technique is reason enough to shoot RAW if you aren't already. There is a complementary post that describes why it's not advisable to do this adjustment with the contrast and brightness slider.