Will anyone be there to see him off? It means so much to them to have a familiar face to send them off and greet them when they come back.
All of the other links are a great place to start, once he gets there and gets situated they will let family and friends know what their email and their mailing address.
Care packages are a life line to home, getting a box means everything to them. A friend of mine that's stationed I send him Phone Cards so he can call me, I send Capri Sun juice to him, crystal light packets, crackers and cheese, little mini packs of cookies, try not to send anything with chocolate in it or on it as it melts, magazine's, books, mini containers of shampoo, soap, etc. Socks are always needed they get a form of jungle rot or foot fungus from the heat and their boots.