One Kings Lane is a members-only online shop that offers sales for 72 hour stretches. Sign up here and you'll receive a $15 credit to your account, which can also be applied to shipping. Once you sign up you can choose to refer other members, and each referral will get you more credit!
I've checked out the site occasionally, and although a lot of the stuff is pretty pricey, you can find some decent deals. Right now you can order 10 birthday cards from Tiny Prints, plus a gift code for 5 free personalized cards from their website for $15. With your credit you'd pay only the $7.95 for shipping, not a bad price! Zak Designs also has a few items priced around $15, so once again you'd only pay for shipping. Or you can hold onto your credit til something cheap comes around and you can score something for free!