NASA ISS App
FYI, by far the best content I have found is the NASA ISS app. Wow. That's the one I demo for all my friends. I want to explore places and things (and places without dragons and cute little animals). The places can be real or imaginary, but they must be rich in detail. We need more content like this.
BTW, in the ISS app they really need to implement two handed movement to change orientation of the view; it would really up the immersion if they did.