Alert shoppers know that gift cards are a little bit of a scam, and a copout as well.
What to do if the last minute has arrived and all you have is the internet and a printer?
It will certainly have far more impact (and less breakage) than something from the iTunes store.
Another thought: order a book that, in January, when it's quieter, will make some serious change. What a great way to say, "I care about you, and I think you're smart."