I rented a 4-pose photo booth that printed out two identical strips from Plan-It Interactive. This was a big splurge, and it was so worth it! The photo booth strips started out pretty tame, but as the evening wore on (and the alcohol from the open bar kicked in) the strips got better and the guestbook entries got funnier.
The company was great about answering my emails and coordinating delivery - they were very professional. Two people delivered the photo booth, set it up, and then maintained it all evening. And they helped all the drunkies work the photo booth machine - a very important task toward the end of the evening.
I liked the 4-pose, 2-strip prints because it meant that I got to keep a photo strip, and guests got to keep the other half. The lady that was tending the booth was really good about insisting that at least half went into our book. I'm not sure if I ever properly thanked her (she was so nice), so thanks, nice lady!