Here’s a terrific visualization of all the multiple-planet systems discovered by the Kepler spacecraft as of February 2, 2011. The planets’ orbits go through the entire 3.5 year mission. The different colors represent different sized planets — “hot” colors are the big planets, cooler colors are the smaller ones, relative to the other planets in the system.
And the creator (dfabrycky ) also put together another visualization of just the small systems, too:
