I used this free program called GIMP, which is a freeware program anyone can download and even edit (the program). It much of the same options as Photoshop, though it isn't supposed to be a copy of it. I got the instructions from [daily dose of imagery] and simply did it myself on GIMP after using Autostitch (another freeware program) to stitch together the 360 panoramas.
[Update 2015]: This are incomplete 360 curls - not real 'planets' or stereographics. These were my first attempts at doing such, not having fully followed the instructions I'd linked above to [daily dose of imagery]. You need a 360x180 degree panorama - otherwise known as an equirectangular - to get the full ground or sky in the shot, plus the plugin Flexify to put it into proper stereographic projection (Photoshop or GIMP can do this on their own but you get a 'globed-in' effect that squashes anything protruding from the ground into the sky).
I'm doing much more soon.