User tracydanger on Instructables has thrown up a neat guide to consolidating all those bonus/membership cards in your wallet. In a nutshell, Tracy took all her bonus cards in her wallet (like CVS, Shop Rite, etc.), scanned in all the barcodes, labeled each one, and printed them out into a nice, convenient sheet that is easily accessible.
Don’t have a scanner or you’re just flat-out lazy? Check out this site where you can enter in the barcodes and have a card generated for you.