Popular Science is running a piece on an apparent surge of activity surrounding Area 51/Groom Lake. The article takes the time to run through the latest rumors that surround the site, and includes a nice gallery of proposed ultra-secret airplanes.
Of course, no discussion of Area 51 is complete without a mention of the legendary (in more ways than one) Aurora, which is, of course, the subject of many speculative articles on the Internet.
I should point out that many of the projects on this page could actually be the same aircraft.
Previously on pf.org: Well, This Explains A Lot (Or, Gov’t Keeps Top-Secret Space Plane Hidden For Decades), No Word on Mountains Made From Mashed Potatoes, Though