I was never able to find decent panoramic stitching software on a Windows machine so you can imagine how surprised I was to find something much more than decent on a Mac - DoubleTake is absolutely fantabulastic. As you can see from the screenshot - I just dragged 6 images onto DoubleTake and it done the rest! If you don't like the results, you can move around the images until you achieve what you want.
You obviously have to have decent images to start with and the Cannon IXY digital camera series comes with a feature which allows you to take panoramic images. the camera does come with stitching software but does not come close in quality as DoubleTake.