SRTM data is only available in a higher resolution for USA.

Original SRTM

Shuttle Radar Topography Mission (SRTM) data products

Free USA 1/3 arc second resolution (10m)

Radio Mobile download site 1

Radio Mobile download site 2

Radio Mobile download site 3

Radio Mobile download site 4

Source: USGS NED 1/3 at Seamless data distribution system

Free North america at 1 arc second resolution (30m)

Radio Mobile download site 1

Radio Mobile download site 2

Radio Mobile download site 3

Radio Mobile download site 4

Source for USA and Mexico: USGS NED 1 at Seamless data distribution system

Source above 40N: Shuttle Radar Topography Mission (SRTM) data products and non published SRTM for Canada

Source for Northern Canada and void filling: Natural Resources Canada CDED at Geobase

Source for Northern Canada and void filling: Natural Resources Canada CANVEC at Geobase

Source for Northern Canada and void filling: ASTER