Just discovered Multimap. I'm amazed I haven't found it before being the map freak that I am. Anyway, it's like mapquest, but of the whole world and without trip planning options.
Other map freaks may be interested in these two sites too:
Status Graphics, using the same server software, indexing the availability of USGS geo-spacial data. (More of a professional index to the data in the National Map Viewer.
Finally, my favorite, which I use to take virtual vacations those three or four times a week I feel burned out, World Wind. If you're one of the geeks who spent three days straight doing Mandelbrot zooms, this is way better. There are lots of nifty overlays, but true fun in World Wind is that it incorporates elevation data so you can see landforms in 3D. Don't try this with a dialup. If you download the 1.2d patch, you can load in a Mars addon to really get away from your troubles.
Now check out Bill Gates' house. If you use World Wind, click this and it'll take you to Bill Gates' house. (Use the layer manager to turn on the high-res urban area photos.) If you can also use Teraserver link to see a flat version. His house (estate) is about 40% up from the bottom of the image, and it looks like three houses with a big dock. If you zoom out two levels and click the USGS quad images you can see what it looked like before it was built. Out another zoom level and click the USGS topo maps to see the elevation data -- its actually on a steep hill.