What I found to be extremely fun is that half of the people (Male and female) put their room keys in a bowl. The other half then pick a key and go to the room with the owner of the key and have sex. This is a very good ice-breaker at the start and ensures that the guys do not JUST have sex with the girls, but also get to know each other better.
OH well, if it makes you feel better you can start with a prayer,