Adobe Lightroom 1.1 has been released and is available free to anyone who purchased version 1.0. You can download the upgrade from Adobe's Lightroom Website.
Adobe Photoshop Lightroom was released last year and was created so that (professional) photographers can quickly and easily manage, adjust (like changing exposure, white balance, saturation and the like), and present (think Slideshow) large numbers of digital images.
Lightroom works like Apple's Aperture in that it doesn't change the underlying RAW photo files. This is very useful because you can always go back to the original image - if one of your modifications wasn't right, or you decide to try something different. With programs like Paint Shop Pro or Photoshop, once you save over an image, the original is lost forever. (This is why I recommend you make a backup of your images straight from the camera first before making any modifications).
Lightroom 1.1 adds a few new features including RAW support for more cameras, improved noise reduction and sharpening capabilities and a new Clarify control. The Slideshow feature has been improved too.
The price is hefty, so if you don't have the need to manage large numbers of photos, then cheaper programs like Photoshop Elements would probably be more suitable.