An easy way to sign your letters is with an autograph machine. These machines are usually located near the entrance of restaurants and hotels that have signed photographs of famous people for their guests to take home as mementos. They are also found in some gift shops and sports stores. The machine reads your signature card like a credit card, so there's no need to fill out any forms. It prints a copy of your signed photograph on photo paper which you can pick up at your photo shop. Then just throw away the machine part and use the signature for future letters.