?Sponsorships, who would I address the letter to?

Answer 1

I wish you were a wee more specific in your question. Sponsorships for what, and to whom are you writing?

If you are writing to big companies, you may want to call them first and ask them who is the best person to address the letter to. Companies like Coke, StarBucks, Pepsi, Old Navy, etc etc, have entire divisions devoted to charity and donations.