Marble

From a few minutes of fiddling with this program I am very happy with it. It has an Earth, Moon and night sky to view, with Earth having a lot of textures (topographic, OpenStreetMap, old map, satellite, night, temperature, ...). There is a great amount of info, places, route planning, and a ton of plugins that add photos, Wikipedia articles, weather info, even satellites flying above the Earth. What I especially loved were different projections aside from the traditional globe view - really great for education. The only downside I found was the absence of high-definition satellite photos, but if you're fine with this, definitely give Marble a try.