As long as you're willing to do a little work, you can get into many concerts, plays and conventions without paying a cent. Just sign up to be a volunteer, suggests personal finance blog Wise Bread.
Many large events will hire volunteers to serve drinks, take tickets or handle questions from attendees. Signing up to perform those tasks will obviously mean you won't get to just kick back and have fun the whole time, but event coordinators usually give volunteers a chance to go enjoy some of the main attractions for free in lieu of actual payment.
Great Ways to Save Money by Volunteering [Wise Bread]