Well, if you were in the US or interested in US locations, the answer is emphatically yes: http://nationalmap.gov/viewer.html
For Australia or Europe, or other parts of the world, I'm sure there are sources but I'm not sure where they are... however a little looking around reveals that you can find SRTM data at (I think) 30 meter resolution here: http://eros.usgs.gov/
There might be better data somewhere - for the US data in my first link you can get it down to 10 meter resolution, I'm not sure what is the best available in the rest of the world. You could also ask around on forum.flightgear.org for sources, a lot of those guys are based outside of the US.
You also might potentially want to take a look at my original "T3DTerrainMaster" project on github, http://github.com/ChrisCalef/T3DTerrainMaster
just for ideas on how to import the height data, although I'm sure you can figure that out easily enough on your own.
Good luck, let me know how it goes!