This is my second submission to this site. Both events occurred in the same general time and area, in the mid-1990s near Vandenberg AFB. They're the only two sky-related sightings I've ever seen, but a LOT of other weird stuff happened around VAFB in the 1990s (sounds, electrical/communications interference, etc).
For this event, I was sitting with five friends in a hot tub on the air force base itself (military housing). It was probably around midnight, in late summer. There were three girls and three boys present, ranging in age from 15 to 20. It was a clear night, and we were looking up at the stars and talking. One person noticed what looked like a star begin moving around in the sky, and pointed it out to the rest of us. At first, we assumed it was a plane, but it didn't have the flashing strobe light on it, and it was spiraling around so erratically that it didn't seem possible that a human could be flying it. We all stared at it, totally enthralled, trying to figure out what it could possibly be, and then it stopped moving and split in two. We all gasped/screamed, but still kept watching.
What had been one weird star was now two of them, and they began the crazy spiraling movements again, almost like they were dancing. This went on for maybe another minute or so, and then one of them just vanished -- seemingly blinked out of existence -- followed immediately by the other one. We all confirmed with each other that we had just seen what we thought we saw, and spent the rest of the night arguing over whether it was aliens, ball lightning, or some kind of super-secret military craft.
The entire event lasted probably 5 minutes. The objects didn't make any noise, and they weren't at all colorful. They just looked like dancing stars. I still have no idea what we saw that night.