Update: The simplest route is probably to just bypass the US site get it from Japan Space Systems: http://gdem.ersdac.jspacesystems.or.jp/index.jsp
Selection can be made from the Search page by clicking tiles, drawing a polygon on screen, uploading a shapefile and entering coordinates. Max tile selection is 1000. The first 100 tiles can be downloaded right away (depending on how many other users are also doing so; 16 max), and the rest are queued up for processing when there are system resources free. You have 72 hours to download from the queue before it is cleared.
Registration is free, though lacking in some of the features we've come to take for granted, like "that username is already taken" and "forgot password?". I suggest using your email address for username.
(Thanks to Ben Discoe for the tip: http://vterrain.org/Elevation/global.html)
A few years ago I cobbled together Backdoor to US Seamless National Elevation Data which may or may not be still relevant. The nutshell is:
where this is your region of interest north,south and east,west in
and this is data set to choose from, in this case “National Elevation
Dataset Alaska (NED) 2 Arc Second”
However don't discount old fashioned snail mail:
“You can order the entire U.S. in 30 meter resolution in either
ArcGrid or GridFloat format. The data will be provided on a 250 GB
external drive at a total price of $1005.00. This includes shipping
and handling. This will cover the Conterminous U.S., Alaska (at 60
meter res), Hawaii, and the territorial islands. We no longer provide
this on CD or DVD media.”
An incredibly good price in my opinion.
The contact address is firstname.lastname@example.org
Data and Applications Support Department
Science Applications International Corporation (SAIC) at
U.S. Geological Survey - EROS
(Earth Resources Observation and Science)
47914 252nd Street
Sioux Falls, SD 57198-0001