I agree with boozebin, Amazon gift cards are a great idea. If you don't have an amazon prime membership, get one. This comes with free 2 day shipping on many items. It paid for itself many times over in terms of shipping costs for me.
Here is the list of the most popular items I have heard freshmen ask for or are sent after A-day
1) Computer monitor (USAFA guidelines)
2) Printer
3) Printer ink
4) Ski gear (snowboards, skis, jackets, pants, gloves etc.) and passes
5) Cell phone/Smart phone
6) Gift cards (amazon, food, etc.)
7) Humidifier (dependent upon the squadron - after A-day they can find out if they can have one)
8) Watch (USAFA guidelines)
9) Food !!!!! (snacks for room after A-day - lots of choices on amazon with free shipping by amazon prime)
10) Sleeping bag, pillow & sleeping mat that is easy to roll up and store (they don't have to mess up the bed once it is perfectly made to standards)
11) Living picture frame (the one with the saved photos that flip through them. It would be one of the 2 personal items they are allowed to have after A-day)
12) Sunglasses (non-reflective USAFA guidelines for after A-day) As for the sunglasses, I wouldn't advise getting expensive ones for after A-day. Many are lost or broken during the first year.
13) Storage bins (specific to storage area dimensions in their room)
Even if he were to get all these items for graduation. He would not be allowed to have them till A-day. So lots of gift cards he can use to either order on-line or shop with at a local store (sponsor may take him or her to a store if requested - walmart, bestbuy are a couple of the large chains nearby)