Microsoft Research has released "Group Shot", a free download that helps users create a "perfect" group photo out 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.
Can't wait to try it out - My recent trip to Brazil has generated some perfect test files for Group Shot.
Not surprisingly, Group Shot requires Windows XP. I will post my usage results later in the week.