For this type of thing, I use J&S Photo Service in Chicago. I'm in Chicago and like having someone local for certain print jobs. I also send my headshot customers to them. Jerry is the owner and is a great guy. They do fantastic work. www.jsphotoservice.com
I use Bay Photo through my SmugMug Pro account for selling prints.
Just a word of advice from 25+ years in professional sales (computers, insurance, real estate). Follow up with a phone call to each person/business you mail a card to. This will approximately double your sales ratio from the cards. Good luck