It's not free, but it's cheap enough, and great: http://www.clickheredesign.com.au/software/ check out this guy's HDR photographs, some truly nuts stuff: http://www.flickr.com/photos/stuckincustoms/ he uses a tool called photomatix to tone-map images into HDR files. Cross platform as well., and has a free basic version. You can also simply open an equirectangular image in photoshop, go to distort>polar coordinates>rectangular to polar and it will magically transform it into the mirrored ball format.