Jonathan de Ferranti maintains Viewfinder Panoramas, which features some interesting discussion of DEM quality issues and virtual globes, as well as his own DEMs for download, and information on other sources of topographic data. Well worth reading, and especially viewing his visual comparisons of how well different datasets (including GoogleEarth) capture some well-known mountains. The image above shows (or rather, doesn't show) Everest as rendered by one of the popular virtual globes...
