George Jardine was part of the team at Adobe when Lightroom was first being developed, so his knowledge is incredibly deep. More than that, though, he has an uncanny ability to explain things in easy to understand bite-sized bits. Starting with the basics, he builds on that it give you a rich understanding of how to get the most of the program. This overview of the Lightroom tutorials is succinct in explaining his approach.
You can purchase his individual series on the Library Module, Develop Module and Location Workflow and Catalog Management on DVD from Amazon.