A few days ago the
Astronomy pic of the Day featured this in an animated GIF which showed all the satellites and then zeroed in on the International Space Station. I just pulled out one frame of the animation because I find it so fascinating.
It turns out that there are two common locations for satellites: low earth orbit just out of range of the atmosphere, and geostationary orbit, where the satellite stays over the same point on the equator. So the outer ring there is made up of the geostationary satellites which revolve around the earth at the same speed as the earth.
The color code:
blue = weather satellites
yellow = communication satellites
green = scientific satellites
cyan = navigation satellites
black = secret military satellites
not indicated = georgia satellites