The USGS site is good but dosn't include much world-wide DEMs. This is THE site for all your GIS info: http://www.gisdatadepot.com/ Takes a little time to figure the site out as there is so much available but you can get DEM/TOPO/ORTHO/etc,etc for free download (or burn to CD ay minimal charge) for almost anywherein the world. There are also many free utilities and tutorials. You can spend a lot of time here so get a cup of coffee first.