I have a bunch of store cards with barcodes on them hanging on my keychain. Every now and then I won't have my keys when I'm in the store. I once saw someone with an iPhone who had an app that managed those bar codes. Is there anything similar for the droid?
I've never used it but I remember reading about Key Ring Rewards Cards. Try that and see what you think.
Edit: I also tried searching the market for "loyalty cards" and came up with this list of apps. I was going to specifically name some but as I haven't tried them I thought it best that I just give you the list. Seems there are quite a few that will help you manage your cards