Hugin is a free panorama tool, or rather a front end for a set of panorama making tools. It’s not totally fire and forget, but then again what panorama software is? And the good thing about this utility is the ability to tweak settings to the nth degree, which means you’ve got a better chance of getting a good result if some of your shots are a little dodgy. Don’t forget to download and install autopano too. There’s a useful tutorial on Lifehacker.
When taking your series of photographs, try to get about 20% to 30% overlap between shots, so you’ll have enough detail to stitch images together. Some lenses have blurry performance near the edges, so you might want even more overlap to ensure the mosaic will feature your best detail from the centers of each image. If there’s a principal feature in the scene, try to capture that feature completely in just one of the images.