It's very possible that you or someone you know has a loved one in active duty overseas. They are likely reachable with normal web based e-mail accounts such as gmail, yahoo mail, hotmail, etc. There are methods by which you can communicate with others in the armed forces via the internet. Letters from home now can take on a whole new meaning.
Red Cross Let's Say Thanks Soldiers Angels
There's even the old standard - pen pals:
Pen Pals for Soldiers Military Pen Pal
Be sure to follow the instructions regarding packages. There are specific rules for sending gifts and items other than letters.
This is a way to show your support for the troops.