College admins who run freshman orientation have the same goal as conference organizers who bring together 300 strangers for a long weekend retreat: facilitate rapid bonding among all the new faces.
The way to do this is not to rely on cheesy ice breakers. Instead, I think you want to cultivate connections by highlighting the common bonds among different sets of people. If two people both happen to be from the same small town in Wisconsin, they should each be made aware and linked up at the conference or in the first week of school.
I've seen three best practices.
First, all attendees or new students should complete a detailed questionnaire before arriving. In it they should list their interests, favorite books, movies, heroes, and what they do on Sunday afternoons when they have nothing to do. Solicit tons of information from each person. Then, on the first day of the conference or school, distribute a print facebook of each person which lists their answers to the questionnaire. (Eventvue does this for conference organizers.)
Second, since group dynamics can distort people's behavior and result in inaccurate first impressions, emphasize one-on-one conversation in those crucial early bonding moments. The best way to do this might be speed dating — five minute conversations with every other person.
Third, make everyone wear nametags the entire conference or first week of school. Enforce this rule. Knowing someone's name is the first step to getting to know the person.
Bottom Line: If you're running a conference or orientation session, don't leave networking and bonding to chance. Cultivate it!