When I was going to buy my Droid X, I knew BestBuy was going to be selling it so I went on cardpool and bought two 100$ cards and got 6% off of 200 from the phone. Its a great service if you know your going to spend the money and want to reward yourself for planning ahead.
I'll also say that I'm glad Carpool exists to limit breakage to some extent, but I'd be much happier if gift cards were gone altogether. Your discount notwithstanding...
I understand that you, and only you, knows best what you desire and that the best I can do to help you is to give you the most universally desired means of exchange.
Gift cards are a ripoff and if you give them you are (normally) doing a disservice.
(FWIW, I actually agree with you, and I imagine there are a lot of others. The hardest part is interacting with those who don't view rationality as an appropriate filter for a celebration, especially celebrating things like 'your not dying in the time it took for the earth to complete a full rotation of the sun', or 'a family-centric federal holiday to mark an apocryphal historical event that has developed societal importance'.)
Perhaps, encase the cash in something that, while not very expensive, required a lot of advance thought/planning?
For example: the enclosure-with-cash needed to be ordered long in advance. And also, encased inside with the cash is some dated and/or custom artifact, such as a personalized note or recommendations of things to buy.
Overall, it sends the message: I rationally want you to buy what you want, but I didn't just thoughtlessly drop a bill in an envelope at the last minute. I've been thinking of you on this gift-giving occasion for a while.