Finding terrain maps...

I'm looking for a website or company that either sells or has free terrain data maps. The USGS (United States Geological Survey) does not seem to have any, or I cannot navigate their site well enough to find them.

This is all for a voxel engine that I've been tinkering around with. Scale of the map does not matter because I can smooth out the large changes in height through bi-linear interpolation, altering the cell size of the world, and by producing noise in the height data.

I have spent weeks and months trying to find terrain maps to no avail. NASA site is large and has plenty of photos but I could not find any useful maps, especially ones that I could download legally.

weird... i wouldn't have figured they'd have a file format standard for geographical mapfiles... the more you know... oh, i'll ask a geography teacher at my school... i doubt he'd be a computer nut like we are by coincidence tho...

After a bit of rummaging around, I found this
http://directory.google.com/Top/Scie...y/Cartography/

Thanks, Salem. I cannot figure out why I've had so much trouble with my research, but before posting this question I can assure you that I just about exhausted all my resources. Perhaps I was just searching under the incorrect words, phrases, or something like that. Sometimes I can find just what I'm looking for on the web and others....well you get the idea. Looks like I've been given a multitude of sites to search.

Again, thanks a million.

Also, doubleanti, I'm not sure there is a standard type of geographical file format. One site listed over twelve to fifteen different types of data formats for geographical data. None of them looked very difficult. Should not be hard to code a base class for the i/o and derive from it for the various formats.