Andrew Kramer of Video Copilot once again puts a lot of effort into a completely free plugin for Adobe After Effects, which can synthetically create whole planetary worlds (but also just realistically the earth).
He doesn&t give away the plugin (including a simple installer for Mac and PC), but has also produced a very in-depth tutorial that demonstrates numerous finesses of the parameters in detail using examples.
Also not unimportant: No further plugins from third parties are needed to create your own, worth seeing planetary journeys. And on top of that there are numerous free textures (among others from Earth) on the project page. Even GPU support has been integrated. What is finally possible with Orb is shown in the following trailer in a short run: