OK, forget all the rumors of black projects, at least until someone gets a photograph of one at Groom Lake. This page deals with planes spotted at Groom Lake other than Janets and security choppers.
This plane was spotted October 12, 2004, between the first and second session of Red Flag. Based on the size of the image, the plane is about 14 miles away. The top image is as the plane appeared on the color slide film, while the bottom image is the "red" channel (which turns the blue sky black) converted to gray scale.
This plane in the next photograph is known to be a SU27. In the upper left corner, the plane was converted to grayscale and turned white to match the unknown plane. In the upper right cornet, the tail section was made lighting to match the lighting of the unknown plane. The bottom two photographs are blurred versions of the upper photographs. The idea is to match the silhouette of the unknown plane with the SU27.
Note that SU27 photo targets for Predator training can be seen here.
These are "external" websites with worthy Groom Lake birds. I could link to the photos, but that is just so not cool. ;-)
Here we have the SU27 with N105TB chasing it (April 2003)
http://gator3.mysite.wanadoo-members.co.uk/tikaboo_peak_8apr2003.htm
See the links to the mystery plane, which appears to be a SU27 as well. This documents the SU27 being at Groom since October 2001.