Lightroom Getting Started guide by Adobe
Adobe offers free Lightroom Getting Stared guide from Photoshop Lightroom Design Center.

This is 78 pages long PDF file that covers:
- Overview
- Library: Getting Images into your Library
- Library: Viewing & Using your Library
- Develop: Image Adjustments
- Develop: Exporting Images
- Slideshow
- Web
Tutorial is available in 2 resolutions:
- Low resolution, which is only 5.4 Mb, that is best suited for quick download and reading from screen;
- and High resolution, which is whole 64 Mb large, best suited for printing.
Enjoy!