Online Crayon Physics Flash version of stuff from here and here. No download needed (vs. prior posts) and totally addicting.
Fireballs are not altogether uncommon. They are often associated with known meteor showers (and other times not). They are sometimes "earth crosser" asteroids, cometary debris, or simply man-made space junk. Sometimes they are extremely well documented. The March 7, 2003 Park Forest fireball/meteorite (pdf) was recovered and recorded by police car cameras: (AVIs: 1, 2, 3) Perhaps the most incredible is the one that got away on August 10, 1972. Recorded by many still and movie cameras as it was seen in daylight over the Grand Tetons, it was also recorded by a previously secret satellite during it's 1-1/2 minute skip off the earth's atmosphere. See also: How to observe, and report fireballs.