This Quicktime movie, from the Astronomy Picture of the Day site (APOD), shows the moon crossing the sun from the STEREO B satellite.
http://antwrp.gsfc.nasa.gov/apod/ap070303.html
The STEREO A and B spacecraft will orbit the sun from an orbit closely (but not exactly) matching the Earth's orbit. One will travel in front of the earth, and the other behind it. The distances will gradually increase, so that we can see solar activity from three different angles. At some point, many years from now, they will encounter Earth again. What happens then, I don't know, but by then they will have completed their mission.
Austin
That was awesome!!!!!