Product Description:
Adobe Photoshop Lightroom 3.0b1 - Import, process, manage, and showcase your images.
Adobe Photoshop Lightroom software is a digital darkroom and efficient assistant designed for serious amateur and professional photographers. With Lightroom, you can organize, enhance, and showcase your images all from one fast and nimble application that?s available on Macintosh and Windows? platforms.

Mac System Requirements
The minimum system requirements for Lightroom 3 beta are as follows:
Intel based processor
Mac OS X v10.5 or 10.6
2GB of RAM
1GB of available hard-disk space
1,024x768 display

Official Site:

http://labs.adobe.com/technologies/lightroom3