Via DCist, another organization dedicated to linking Montgomery and P.G. County suburbs with light rail. See also the Inner Purple Line. My predeliction is for heavy rail, but I look at the twisty alignments that are being discussed, and I consider the graceful, older neighborhoods involved, and I begin to think that light rail is the better choice.
Compare the Anacostia light rail project in the District, for which ground has been broken (but, disturbingly, with little progress to report since 2004), and the Columbia Pike initiative in Arlington, in the planning stages.