eBillme offers a $15 mail-in rebate for Amazon $100 gift cards when you buy your card from them and pay at your bank or online. Offer expires January 15, 2011. For first time use of eBillme only. Restrictions apply. See site for more details.
If somebody do not trust the cashback thing too much, you can use the code AFF100 to get 10% off, but this will void your cashback.