Hugin is a great (free) program for making panoramas. You'll have to google it, I'm not digging up the link.
Yesterday I made
this (be careful, 42 megs, 98 inches wide) from 18 images that were over 5000 pixels wide each. Took less than half an hour and the only places I could tell it was stitched together was a slight shading difference in the sky where I shot at a wider angle to eliminate a person.
The trick to a smooth pano is to take the shots at about 20 degree increments (overlap the shots by 1/3 on each rotation). That way the program has more to reference from the previous image.
Good luck.