First you need a soldier's name and an APO address for him/her.
Sometimes the best way to find that is to ask friends and relatives if they know anyone serving in Iraq or Afghanistan, and get it from them.
Our APO's are held to a few in our group that I know well enough to trust because I've dealt with them other times in the past. You can put together care packages, send them to one of us, and we can ship them overseas for you.
Right now we're concentrating on movies for a new base we're in contact with and Christmas stockings and decorations for a few bases. McLynnan has point on Christmas in Kirkuk and I'm going to start a thread right after the election to get Christmas cards and letters/notes for several bases in Iraq and one in Afghanistan, plus stockings.
There are restrictions on what can be sent and how certain things should be wrapped to prevent leakage. And the boxes we send to our APO's have to have a customs form filled out.
If you get an APO and soldier name from among friends, I'll be happy to give you more precise information on wrapping and shipping. If your soldier agrees you can use him/her to receive boxes for all those in his/her unit, or he/she can make arrangements for you to send to the company commander or chaplain.
Let me know if you need more help.