To date, the Kepler space telescope has probably identified at least 2,299 planets orbiting around other stars. 2,299 planets is a lot of planets, obviously, but this simulation that puts every single last one of them in orbit around the same star is a very visual, albeit very implausible, way of illustrating how many planets are out there.
Before you watch the simulation below (which is by Alex Parker, a postdoctoral researcher in planetary science at the Harvard-Smithsoniain Center for Astrophysics, aka Someone Who Knows What He's Talking About), there are just a few things to keep in mind.
First, everything you're seeing here is as accurate as we have data for. The relative sizes, orbital distances, and orbital periods are all real, albeit normalized to the one single sun in the sim. Even the colors are representative of estimated surface temperatures.
Secondly, all of these planets are, by definition, planets that Kepler can see. This means that they're not necessarily a representative sample of all of the exoplanet that are out there, since Kepler has an easier time spotting large exoplanets that are close to their parent stars. At the end of the simulation, you'll see three white rings, representing the orbits of Venus, Earth and Mars, respectively. Kepler hasn't spotted many planets out at those distances, but that doesn't mean there aren't any: it's more likely than not that there are billions of 'em out there that we just haven't seen yet.
What we'd love to see next would be a simulation of what would happen if you flipped the physics switch to "on" and all those planets suddenly had to deal with some serious gravitational attraction. In other words, they'd probably all smash into each other all at once, and then whatever's left would end up diving straight into the star. Good times, yeah? Ka-BOOM!