GIMP

Filters > Distorts > Polar Coordinates

Uncheck "map from top"

Find your own image to map on panoguide.com then locate the original jpg using this example:

http://www.panoguide.com/gallery/1535/
http://www.panoguide.com/gallery-images/1535.jpeg

Examples / pictures to use

Other Examples

Even more examples

How it works