According their Facebook page:
52 Weeks of Mail, brought to you by Etsy Greetings Team, is designed to encourage people to be more intentional about relationships and keeping in touch with friends and family by sending out a card or letter each week, for the next year. I don't know about you, but I LOVE getting a personal, hand-written card or letter in the mail.
Throughout 52 Weeks of Mail, we are asking everyone to commit to sending just ONE card or letter each week. You can send more than one, of course! 52 Weeks of Mail BEGINS on October 9th, 2011, and ends on October 7th, 2012. Please feel free to blog about this event, or share it on your Facebook page. Share it on Twitter, or any other social networking site too!