I've updated my tutorial, on making mountains in Blender using heightmaps, for Blender 2.5.

http://johnflower.org/article/tutorial-make-mountains-blender-25-height-maps

As well as showing how to convert real world heightmaps into mountains, I've added heightmaps for downloading, links to high resolution source files, and instructions on preparing them for Blender.

The new link for the tutorial is http://johnflower.org/tutorial/make-mountains-blender-height-maps.