There's still time to sign up to participate in the 2011 International Postcard Swap for Families hosted by Playing by the Book. My family participated last year, and we received some really interesting postcards and several wonderful book suggestions. Sign up ends on May 17th.
Also, if you like giveaways, Playing by the Book is currently giving away a Where’s Wally? The Phenomenal Postcard Book. The giveaway ends in less than a day and the contest is open worldwide. Enter by 6:00 a.m. May 11th (UK time).