I wanted to add a feature to caltopo.com that would show you the view from a given point and identify peaks/features. As I started playing around with how far above ground to place the "eye", I realized that going tens of thousands of feet up and way back made for some neat terrain visualization:

West Slope Sierra
East Slope Sierra
North Cascades NP
Front Range
Glacier NP

There are still a few quirks to work out, but at the rate I'm wasting time playing around with this, I'm not sure when they'll get fixed. The USGS data I'm using for peak names puts them up to a couple hundred meters off and at the wrong elevation, so a few of the labels show up in funny spots. Also Internet Explorer won't rotate the labels 45 degrees, so they all interfere with each other.

At some level this is maybe just a slow and poor knockoff of Google Earth. However GE zooms in by moving you around the globe, and I don't think it allows your brain to process large-scale terrain in the same way that zooming in from a fixed point does. For me, at least, these aerial maps give a perspective more like the relief models at NPS visitor centers. Enjoy!