Downloading SRTM data
Update: I think wget would be better, i just don't use it very often:
wget -r -A.zip http://dds.cr.usgs.gov/srtm/version2_1/SRTM3/
Also see for some retrieval wait options (if you want to be courteous): https://superuser.com/questions/178297/wget-terminates-unexpectedly/178326#178326
You could curl the files with a little bit of text editor work.
For curl, the man page is here: http://curl.haxx.se/docs/manpage.html
Download here: http://curl.haxx.se/download.html
I think there are throttling and retry options (check the above-mentioned man page).
curl -O http://dds.cr.usgs.gov/srtm/version2_1/SRTM3/Australia/S11E119.hgt.zip
curl -O http://dds.cr.usgs.gov/srtm/version2_1/SRTM3/Australia/S11E120.hgt.zip
curl -O http://dds.cr.usgs.gov/srtm/version2_1/SRTM3/Australia/S11E121.hgt.zip
curl -O http://dds.cr.usgs.gov/srtm/version2_1/SRTM3/Australia/S11E122.hgt.zip
curl -O http://dds.cr.usgs.gov/srtm/version2_1/SRTM3/Australia/S11E123.hgt.zip
In addition to Jay's excellent pointers, I would recommend using the --timestamping flag when downloading so you can only get files that are newer than on your file system (really useful when your downloading gets interrupted).
Additionally, using the --no-parent flag means that only the SRTM3 directory is downloaded rather than it continuing up the tree to the other directories.
The full wget commandline I'm using:
wget -r --no-parent --random-wait --timestamping -A.zip http://dds.cr.usgs.gov/srtm/version2_1/SRTM3/
You can download and clip a portion of the SRTM 30m DEM with one command with the elevation Python command line tool.
Install it and perform the self check with:
$ pip install elevation
Check if you have all the dependencies installed (mainly GDAL tools):
$ eio selfcheck
Download and clip a portion of the SRTM 30m DEM giving bounding box as WGS84 coordinates:
$ eio clip -o Rome-DEM.tif --bounds 12.35 41.8 12.65 42
You can use Maperitive to download SRTM tiles automatically and unzip them. Just zoom in/out to the area of your interest and it will download all the required tiles to your disk. And best of all, it's free.
Here's a sample hillshading + hypsometric rendering generated using SRTM tiles in Maperitive:
