Lightroom Training
I've been using Lightroom frequently for about 3 months now and thought i knew the product fairly well until i started watching Chris Orwig's Training DVD from Lynda.com.
In the 5.5 hours of play time, I've learned a great deal and it's definetely helped me to work my way through LR a lot quicker and more efficiently.
If you've been using Photoshop for years (as I have), you may be tempted to think you don't need training (RTFM syndrome), but believe me it's worth the time. Lightroom is a completely different beast from Photoshop (and Bridge) and after the training you'll really appreciate the functionality that LR has to offer. I do!
Here is a link for two books that Chris recommends for Lightroom on his website.
NAPP's Photoshop User Magazine also now includes Darkroom, a supplemental magazine which focuses purely on Lightroom features.