Microsoft Research Group Shot.

MSR Group Shot helps you create a perfect group photo out of a series of group photos. With Group Shot you can select your favorite parts in each shot of the series and Group Shot will automatically build a composite image.
Download Group Shot.
Version 1.03 fixes a few bugs and adds the ability to save results as TIFF and Layered PSD.
Group Shot was developed by
Alex Colburn,
Matthew Uyttendaele, and
Michael Cohen.
Please see our web pages for more information on related technologies.
For more information about the algorithms behind Group Shot, please see the 2004 ACM SIGGRAPH paper
Interactive Digital Photomontage.