Wikipedia has an overview of World Wind-
http://en.wikipedia.org/wiki/Nasa_world_wind

I had it on my old computer, but now just use Google Earth, which does not have realtime images, but is good for looking at places. I don't know which apps on World Wind are actually real time.

For weather, I use NOAA. You can usually get updates on trail conditions by just asking on different websites-the info is probably more reliable than an aerial photo of uncertain vintage.
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