It seems as if many celebrities (sports, entertainment and historical) are now selling signed photos online. This is not an entirely unwelcome trend. Granted, nothing beats a free authentically signed photo through the mail. However, I feel that the days of major celebrities signing and sending a free photo are coming to an end. The volume of mail these people receive must be tremendous, and it would cost a small fortune to handle the mail and send out free photos -- not to mention take a lot of time. My guess is that celebrities such as historical figures just can't afford to honor free requests any longer.
There are several benefits to homepages like the Enola Gay mentioned above: 1. you can be sure it's authentic, 2. the prices are usually cheaper than what a dealer would ask, 3. the photos available are often better than photos you could find to send yourself, and 4. it's easy and fast. Check out my Resources Page for more celebrity homepages.