An open source alternative to PT Gui
Hugin is perfect and free!
For tutorials search in their web hugin.sourceforge.net
For automatics control points (in Windows) I recommed Panomatic aorlinsk2.free.fr/panomatic/
link is broken
For me Hugin did the best job out of at least 10 applications. I stitched 3 sunset images with 3 diffent exposures. Splendid!