I literally just downloaded it and opened it, so I can't tell you anything about how it works yet, but hey, it's free! :)
"Project: Lightroom is Adobe’s effort to engage the professional photography community in a new way, giving you the opportunity to kick the tires and shape the feature set of a new tool being created just for you. Ultimately, we want Lightroom to be truly built from the ground up by photographers, for photographers, helping solve your unique workflow challenges.
We're releasing a preview build now so that you have plenty of time to give us feedback on what’s working for you, and what isn't. Your participation is important. So, don’t delay. Download now and send us your feedback before the Lightroom Beta 2 build expires June 30, 2006.
To learn more, check out the Lightroom Beta 2 Overview and Getting Started with the Develop Module video below which will help get you up and running on Lightroom.
Note: Although initially available as a beta for Macintosh, Lightroom will later support both the Windows and Macintosh platforms. Sign-up to be notified when the Windows version becomes available."