gah, it was so long ago i forgot how i did it. basically playing with polar coordinates in ps. one creates a little planet, the other one creates a warphole. has got something to do with the angle of rotation of the image (yes, I know, bit complicated but nothing too hard). google 'little planet'
Did you use a special program (or lens) to do this, or did you have to merge all of the photos yourself?
Either way, the result is amazing. It makes me want to try one myself . . .