Aurora: The Secret Hypersonic Spyplane

FirstScience.com may suffer from somewhat crappy design, but they have a fascinating article outlining evidence pointing to the existence of Aurora - The Secret Hypersonic Spyplane, long-rumored to be the Mach 6+ successor to the famed Lockheed SR-71 Blackbird, which was retired from service in 1990. (You can see an SR-71 in person at the Air Zoo in Kalamazoo, btw.)

More info on the Aurora is available at This is Rocket Science.