Shala1,
I have not had luck with companies outside our area. They just receive way too many requests. I don't know where you live, or how close you are to a big city.
First, visit your local chamber of commerce. They should have an easy mailing list of their members.
I've had good luck mailing a well thought out letter to businesses, restaurants, hotels, movie theaters, car dealers, car washes, electronic (best buy), hair salons, book stores, ???, museums, professional sport teams.
stating in your letter:
1. what are you raising the money for? (be specific) is it for library books? playground equip?
2. What, where and when is your event? (you need to get these letters out at least 1 month before the event).
3. Put in a deadline. "I hope to be notified of your response by February 14th." After the 14th, start making follow-up phone calls. Don't be surprised if they say "I never received it." Then send the letter again.
4. What will you do for THEM if they do make a donation? Offer free advertising during your event (a poster with their name on it, announcements during the dance, a blurb on your PTO website or newsletter).
5. IMPORTANT... If they do make a donation. SEND A THANK YOU LETTER after the event is over and tell them how their donation helped to make it a success.
Hope this helps.