"Almost half the adult population in the US is rarely or never online. Globally the numbers are closer to 80%." says Postful. One of these is my folks that are never on line is my Mum. I still write her regular physical letters and postcards, her not really wise in the ways of email.
Postful has proven to be extremely useful to me, and I highly recommend their services. Basically it allows you to compose an email to postful, put the physical address of the recipient in the subject line, and they will print it out and mail it off. The price is quite reasonable, and they send internationally too.