Lightroom 3 Learning center

Some instructional videos can be found here:

http://www.photoshopuser.com/lightroom3/

Ars reviews Adobe Lightroom 3

I found this review very insightful and gives a pretty good breakdown of whats new

http://arstechnica.com/apple/reviews/2010/06/adobe-lightroom-3-review.ars

Lightroom 3 book

The official Adobe Lightroom 3 book is available for pre-order from Amazon:

http://www.amazon.com/gp/product/0321680707/ref=ox_ya_os_product

An alternative guide by a well respected software expert is available here:

http://www.kelbytraining.com/product/the-adobe-photoshop-lightroom-3-book-for-digital-photographers.html