Projections used in Panorama Photography
One of the most confusing issues about image stitching and panorama photography, are projections. These are the various ways that are used to project a portion of a spherical view of the world on a flat surface. The wider the angle, the more complicated it gets. Think back to school days and maps. Making a map of the world, on a flat wall pull down, as opposed to a globe.
Depending on the program you use to do your stitching, you may have many options. I just added a page to my tips and tutorials, under the Panorams and Stitching Tips with samples of the same image, using a variety of projections.