Some links I have collected.

http://dds.cr.usgs.gov/srtm/version2_1/

http://asterweb.jpl.nasa.gov/gdem.asp

http://seamless.usgs.gov/

http://glovis.usgs.gov/

http://www.ngdc.noaa.gov/mgg/shorelines/shorelines.html

http://www.ngdc.noaa.gov/mgg/bathyme...tdownload.html

http://www.geomapapp.org/index.htm