This week Target has 4"x6" digital photo prints for 10¢ each. If you go to their coupon page (click here), there is a $2 off 20 prints coupon to use in the store. So if you get 20 prints and use that coupon, you will get 20 for free! I believe you have to process the prints in store (i.e. not upload online).
Cheap gift idea: Buy a photo album or picture frame from a dollar store and fill it with the free prints.