If your want a free or cheap night out (depending on whether you have to hire a sitter to watch your kids) check out the Free Night of Theater 2009.
The annual event does not offer any plays in Pennsylvania BUT does offer several in New Jersey, including one in New Brunswick and one in Princeton. They also offer many in many other states.
All you have to do is go to their Web site and sign up for the free tickets. They are for one night only, and the the dates vary depending on the venue. The Free Night of Theater is offered nationwide on a yearly basis.
If you want to take advantage of this free date, make sure to check it out today or tomorrow. The tickets in past years have disappeared quickly.