Xerox has a site that lets you select a "thank you" card and a message to send to an American serviceman in Iraq.
I picked a card that had been designed by a young Tennessee student. Then I picked a message, signed it, and sent it. I encourage others to do the same.
Just go to http://www.letssaythanks.com/ and follow the directions. Over 3.7 million messages have already gone out!