You can go to local businesses and ask for donations, and most larger chain stores and movie theaters will also give at least a little something- maybe a gift certificate or coupon for a free drink. I do know from my teaching days that Wendy's is almost always good for a few freebies when raising funds for a school event.
Also check out online companies like Sears and Target, or go even easier and use a company like Uearning, which helps facilitate partnerships between online retailers and people looking to raise funds for school. Services like this can save you a lot of time, aggravation and money, not to mention that the process is quite easy.
Go to Uearning.com to raise funds online for free!