I used to run a care package collection at my high school and then was in the military. A few tips:
Hard candies rock! Nothing that melts like chocolate. Mints are so wonderful to receive. Plus they make awesome bargaining pieces.
Baby wipes or personal wipes. It is hot and sticky over there and small, personal packages that can be carried on the person are truly life-savers.
Small handheld games, books, magazines and playing cards (although it goes back and forth on the latter so ask his base commander or whoever is in charge about them). Absolutely nothing with risque material, and religious items are only permitted on certain things so I would avoid that too. Amazon keeps having great deals on handheld games - or a DS might delight! Plus everyone else will be mega jealous.
Personal hygeine items are awesome. Lotion, sunblock, aloe vera, and the like.
Fruit leathers or roll-ups. You have no idea how monotonous those dang MRE's get. These things last and are yummy. Other food items are jerkey (good jerkey is hard to come by over there!), power bars, and his fave gum.
Also, when in doubt, try contacting his base to find out what you can send. They usually have some great suggestions. Keep in mind nostaligic items (does he usually look forward to peanut brittle, ginger bread, or candy canes this time of year? Get a mini stocking and stuff it with Christmas item!).
I know this is a hard time - I have been there - I spent several holidays away from family...receiving care packages not only comforted me but helped me know that I was loved even in times of such hatred. My mom always slipped in newsclippings, sweet stories, or little notes from my younger sisters. It meant so much to me. I still have it all in a plastic bag....best of luck and hugs! He'll be home before you know it!
C.