there are also several good books that cover all different types of B/W conversions. These are three that I have found useful.
Vincent Versace, "From Oz to Kansas: Almost Every Black and White Conversion Technique Known to Man" focuses more on using Photoshop than Lightroom but the linear appoach to learning how to use the tools is well presented.
George DeWolfe, “B&W Printing: Creating the Digital Master Print” discusses how Lightroom can be used to produce outstanding black and white images. I did not pay any attention to the author’s new software tool that is supposed to improve the perceptual quality of the print.
Leslie Alsheimer and Bryan O'Neil Hughes, "Black and White in Photoshop CS4 and Photoshop Lightroom" covers all aspects of black and white transformation using the two key Adobe software products.