The above are the result of PanoLab, Hugin, Calico, and a single shot with a very wide angle lens (Canon’s 10-22mm, effectively 16mm on my Rebel XTi). The first three originated on my iPhone and the PanoLab shot was stitched and originally uploaded to Flickr on my iPhone (though I have since done some color enhancement and reuploaded the photo from my MacBook Pro). Hugin is GPL, the other solutions are less free (in both senses).