Right now if you purchase postcards from overnightprints.com (they have a range of sizes), you can get 100 postcards for $9.95. They're normally $29.95, so that's a sweet deal. All you have to do when you check out is hit the big "ADD POSTCARD SALE" button to the bottom right of the screen on your shopping card page.
If you're getting business cards, you can't get that sale. But you can $10 off your order if you put the code "BC100" into the coupon space on the checkout page, or for 15% (whichever is better for you) you can type in "GRAD1509".
I hope this helps!