There are plenty of great resources for the Lightroom 3 beta. I’ll keep the list below updated as new content comes online
Julieanne Kost on AdobeTV
http://tv.adobe.com/show/what-s-new-in-lightroom-3-beta/
Terry White’s Tech Blog tackles the beta
http://terrywhite.com/techblog/archives/3747
Matt Kloskowski with the NAPP Lightroom 3 learning center
http://www.photoshopuser.com/lightroom3
Victoria Bampton describes what’s new on www.lightroomqueen.com
http://www.lightroomqueen.com/blog/2009/10/22/whats-new-in-lightroom-3-beta-2/
Sean McCormack
http://lightroom-blog.com
Ian Lyons with a Computer-Darkroom Post
www.computer-darkroom.com/lr3_preview/lr3-preview-1.htm
Art P Suwansang from Wedding64.com
www.wedding64.com/lr3b
Gene McCullagh provides
http://lightroomsecrets.com/2009/10/lightroom-3-beta-is-here/
Jeffrey Friedl on Lightroom 3 beta and plug-ins
http://regex.info/blog/2009-10-22/1339
Gilles Theophile on Lightroom 3 beta for our French speaking customers(FYI, the public beta is English only)
http://www.utiliser-lightroom.fr/2009/10/21/bienvenue-a-la-beta-publique-de-lightroom-30/