Most likely you’ve heard of Microsoft’s terraserver. I happened across an excellent alternative today, the acme mapper. Mostly it seems to be the same dataset that Microsoft has for aerial photography, but they also have the usgs topographical dataset stitched into the interface. It all looks very rudimentary/old school, but it works great and is relatively speedy. Check out this close-up of 5th peak in the tongue mountain range. The red target is where I was standing when I took thiscrude but effective panorama shot last weekend.