Io
During one of it's flybys, the Galileo spacecraft
shot a series of images that, due to the motion of the spacecraft, can
be combined into a stereo image. Due to the time between the shots,
Io has rotated a bit, and the features are a little closer to the terminator.
Taking that into account, focus on the left side of the image, and you
can see the "sphereness" of the moon, and get a pretty good feeling for
the location of the two bluish volcanic plumes visible in the photo.
Click on the image for a larger view.
Source page: http://www.jpl.nasa.gov/galileo/images/io/ioplume.html
