Dont think this has been suggested yet...
As I was ordering photos off of Shutterfly.com today I was thinking of how a calendar would be a great idea for a deployed Marine. You can add family photos and personalize it. It would be something neat for him to take along with him before he goes, but if he has already left, you could send the calander with the dates that have passed marked off so he could see how many days you have made it through. And maybe add family/friend b-days on which ever dates or write little notes for him to read in the boxes through the months. A 12 month one on Shutterfly is $19.99 or I guess you could always save a little money and make your own if you have that kind of patience!