Three excellent "primer" books are by Scott Kelby, Martin Evening and Victoria Bampton. Amazon will heve them. Any one or more than one will be very good in getting you started, they walk you through the various features and each offer great insights.
Web sites are numerous. AdobeTV has a lot of Lightroom tutorials. Scott Kelby hosts KelbyTraining.com, a subscription site with a staff of accomplished professionals. That and Lynda.com, another subscription site, can pay off if you can dedicate say a month to work through some of their videos. They both have material for CS5 as well, so once you really get underway with Lightroom, it could benefit you to get some Photoshop training under your belt.
Kelby also hosts LightroomKillerTips.com, a cool place for free "mini-tutorials".
Victoria Bampton hosts a site LightroomQueen.com that is quite useful for resources.
You can also access Lightroom Users forums at Adobe and the LightroomQueen site that can be very helpful. Do a search for "lightroom user forum" and you should get both those and other choices:
Welcome to the Lightroom gang!