I've begun working on an icosahedral planetary random hex map generator. So far I have a simple prototype, showing only land and sea areas, but eventually I hope to use Thorfinn Tait's Mystara tiles and have realistic climate zones. The program actually outputs .SVG files, but these have been converted to .PNG for the web; hopefully in the end you'll be able to edit the maps in Inkscape or Illustrator.

Here's the same planet generated at a range of different hex scales: