I was in and out of the car at some scenic locations along the Hudson and Mohawk Rivers this morning, using both the 17-40mm and 24-105mm lenses. As I was processing, I noticed that two of the images were horizontally lined up almost perfectly without that intention on my part.
I decided to give it a shot with Canon's PhotoStitch software and see how a panorama might come out. Here are the two single images, both five file HDR composites processed in Photomatix Pro and saved as TIFF files.
There is about a 20% overlap between the images which is necessary for the software to combine them. The first image was made at 75mm and the second image was made at 82mm. That's not a large difference but you can see the seam between the shots in the photo below and there is an obvious digital artifact at the shoreline due to the focal length difference. It almost looks natural if you didn't have the original shots to compare it to.
Here are some other shots from this morning.