I came across this ingenious idea a couple of weeks ago when I was looking through some photos of a wedding a friend went to. I thought that is was such a fantastic idea.
The principle is simple. Hire out a photo booth (like the ones you get passport photos taken in) and let guests at your wedding take a variety of crazy, or traditional, photographs. Best of all, you can even get them made into a photo album. Great impromptu photographs. Sorted.
Here is a selection of companies who offer this service:
Get snappy!
Wedding Belles 