A classic is "Real World Camera Raw" (there is a CS5 version out):
Since Lightroom and Photoshop CSx share the same "Raw processing engine" the learnings would apply equally.
Three good Lightroom books are by Scott Kelby, Victoria Bampton and Martin Evening -- one or any combination of the above would be excellent additions to your library.
Then, there are two premier for-pay training sites -- Lynda.com and KelbyTraining.com have Lightroom material.
Kelby also hosts LightroomKillerTips.com which has a ton of useful stuff. And then, AdobeTv has free Lightroom tutorials.
Of course, these are all specifically Adobe Camera Raw/Lightroom-centered resources -- since that's what your are using they should all be helpful. The "bigger picture" of understanding Raw and the fundamentals of Raw processing will work themselves into these books and tutorials. As you go and have specific questions you wonder about, some combination of asking here and googling should get you plenty of info.
And then, spend time in our Raw, Post Processing and Printing sub-forum -- read the stickies and check posts because helpful topics come up there all the time:
Lastly, check out our RAW Conversion Thread for many cool and inspirational examples of what you can work with!