This idea was first posted on the TUAW website but it was just genius enough to repost on Blogintosh. Membership cards from Hallmark, Staples, Blockbuster, Safeway, Petsmart and every other retail chain plague my wallet leaving little room for the large amounts of cash I make. One little Appletard had the great idea to scan the cards and save them in the iPhone or iPod Touch under iPhoto. The cards are still fully scannable and cut down on wallet size an average of .3 inches. Presumably the same could be done for gift cards, you would just have to remember to delete the photo when the card was used up.
Unfortunately this solution will not work with punch cards or stamp cards but give it a couple months and someone will come up with a solution for that too. Just remember you heard the prediction on Blogintosh first.