"I didn't know you could write to "any soldier" and have it get there."
In the good old days (before 9-11) you could do that, but security concerns have ended
that venerable program.
Now you must send letters/packages to a specific service-person and use their military
(usually "APO" or "FPO") address.
See post 3 above; Ragtime Cowgirl and friends can surely get you some specific service-persons
and their military address for you to write to.
And if you still need more addresses, you can find some at this page from my old
hometown newspaper (note that most are not if Iraq and Afghanistan; but I'm sure all
would get a lift from a well-meaning note).
http://www.poncacity.com/spirit/mailing.aspAnd the Hobbit Hole has a care package initiative going constantly...you can send money and letters to one of the Hole Dwellers and she sends them on to a platoon along with all sorts of items like mag-lights and pocketknives and every kind of munchie you can imagine. If someone writes back, then your son will had an address to send to!