This is one of the most amazing videos I've ever seen. The Deep Impact spacecraft launched in 2005, with a mission of firing an impactor at comet 9P/Tempel, to learn what the comet was made of.
After the mission was completed, Deep Impact was retasked to imaging extrasolar planets and another comet, Hartley 9, and renamed EPOXI. Just three months ago, EPOXI trained its cameras back towards Earth, and from a distance of about 30 million miles captured this series of images:
That is a series of images of the moon transiting the Earth, and as far as I know that's the first time such a thing has ever been witnessed. Amazing.