Skybox Program?

What is a good program for making skyboxes?
Prefferrably one that's cheap or free as I do not have a lot of money to throw around.

This is one place to start:
http://www.skypaint.com/

http://www.blitzbasic.com/Community/posts.php?topic=31940

Mortiis is referring to SkyPanorama by Fredborg, and I've just written the loader code to take SkyPanorama's output.
http://www.blitzbasic.co.nz/codearcs/codearcs.php?code=2336