I did a creative eye catching letter, and even with that, it still did not bring in a lot of money... the letters that "worked" did so mainly because an employee worked at that company with children, attending our school, and they brought the letter to the attention of their business "charity" person, i.e. I do think that a lot of organizations out there DO have "community involvement" liaisons, and so forth, but in order to access these funds, the best way to do it is to visit with them in-person, or have someone that you know who works there, give the pitch for you. When we did our coin drive, we made more money by offering our "corporate matching grants" than our "letters" did because either I did an in-person contact or a parent in our school did...plus, the idea of the matching grants seemed like a novel idea to these businesses as a chance to "double their money", i.e. let their donation double in size and do twice as much good!
Whenever possible, get that personal connection by having an employee of the company do the pitch for you because I did hear a lot of "no's", i.e. " we've already made our donations for this year..." or "our donation fund is at zero right now, so we can't help you..." When you've got that person who works for the company making the pitch, it seems to mean more to those holding the purse-strings to help you out.