As Lance pointed out the easiest accessible DEM is probably SRTM-data from NASA. They come in 1 and 3 second spacing (30 and 90 meters respectively). This data is useful if not a too much resolution is expected. There is quite some noise involved (which shows up as little hills and holes). In some areas the data is completely off and seems to be interpolated using the surrounding good data. But whole valleys and peaks are missing in some places. I don't know if this is due the bad weather conditions while the data was taken. The edited version 2 has at least the lakes level for example. Until recently this version was only available in 3 second spacing (SRTM-3).
The following pictures were created using the unedited SRTM-1 data with Landsat images overlaid.
Example 1 Example 2 Here is an example with obviously wrong data, the valley with the place called Selden has no exit. In reality the river flows towards Kandersteg.
Example 3 The same area: The valley behind the label 1578m cannot drain towards Kandersteg as it does in reality.
Example 4 I created those before Google Earth offered the resolution of today. If you are just interested in the 3-D image Google Earth is clearly superior.
In addition to the SRTM data, I have downloaded the 1-degree DEM data from USGS (3 arc second spacing) for the entire United States as long as they were available (I don't think they are anymore). This is more than 1GB worth of data. I also have selected areas of the 7.5-minute DEM (I believe 1 arc second spacing, maybe 1/3 sec.) including the Mt. Whitney area. I am more than happy to send you those. The Mt. Whitney quad (as any other) is less then 2MB. But that would have to be next week as I will be out of town until next Tuesday.
I used a program called
Kashmir to display the 3-D model and overlay additional information, such as the Landsat images. It is a free software that was created by a Japanese guy. Unfortunately it is not very intuitive and the support in English is not that great. I had a buddy at work form Japan who was instrumental in getting this to work. NT-Space (a consortium of NEC and Toshiba) also published a similar program but I cannot find the link right now. As I remember it was also free and just as Japanese as Kashmir (little English support).
Good luck
Kurt