I went to see "Watchmen" with Sean David Morton last night, and on the way back I was telling him about my UFO sighting. He said the same things have been seen in the South Bay area several times over the last few months, including by him. I went to YouTube and found some videos:
It looked exactly like this one, only it didn't change color like this one did. This is footage from last Halloween and Sean saw it:
Here's one with a video testimonial. You can clearly see the ring shape and the slow, tumbling motion. This is from April 22nd of last year:
There's another guy who says they're fake, but I couldn't understand the name of the website he gave.