The raw elevation data in Digital Elevation Models (DEM) format used to be on the USGS site and freely downloadable. The files are huge (at least 2-3 meg compressed in .gz format). Geocomm has a contract to offer them free now. There’s a free registration.
Visit the GEOCOMM Dem Download Site
The only catch is that the downloads are VERY SLOW. They want you to pay for premium downloads. The price is not that bad for one offs and if you bought the entire collection it would be $2,000. Geocomm has a wide variety of other data. You need to click on the green button to get the free download. If you need to find the quad you want to download a good place to check is topozone.com.