I write some terrain generation tools and two of them are free. One is called Instant Islands and is here :

http://www.viewing.ltd.uk/cgi-bin/vi...nstant_islands

the other is a 3D terrain viewer called DragonFlight :

http://www.viewing.ltd.uk/cgi-bin/vi...dragons_flight

The instant islands saves out a Height.bmp and a Height_minor.bmp. You can use just the height.bmp for 8 bit height info or add in the minor for 16 bit height. The viewer takes those two files and also a Color.bmp file (also produced from the Instant Islands) to show the 3D terrain. From those height maps you can create a) the google type color scheme for it and b) view it in 3D pretty fast.

Very recently tho, Waldronate has posted up some fun with Wilbur threads about creating terrain with it so check those out too.