Mike Melvill and SpaceShipOne recently made space history; but, as Donald Sensing notes in his weblog "One Hand Clapping," he is
not the first civilian astronaut.
Neil Armstrong was. He signed on to NASA as a civilian test pilot. When people refer to Melvill as the "first civilian astronaut," they mean, of course, something along the lines of "the first astronaut not to be so via NASA." But that isn't quite so elegant a description.