I’ve recently come across the open source software Xplanet, which will render images of the globe with very realistic results.

I render them in 512×256, 1024×512, 2048×1024 and 4096×2048 resolutions. The clouds information is obtained from weather satellites and is typically around three hours old.

I also use monthly map files so that the snow/ice on the planet is more realistic.

Check out my real time renders at /earth/.