What if postage stamps were really useful

Now you might be thinking "stamps are useful, I can post things with them", and you would be right. When it comes to sending letters, stamps have pretty much got the market cornered, but couldn't we do more with them? I started thinking about new uses for stamps, this morning, when I saw this ecological calendar. Calendars generally have a life of at least 12 months, and often longer if their pictures get recycled into other things. Couldn't we do similar things with stamps. What if they contained a list of upcoming concerts that might appeal to me. I might keep them in my wallet, as a reference, and also send them off to friends as reminders to come to the gig. If we came up with some really good ideas, we might even get to the stage where people just post stamps, i.e. not attached to anything, the stamp itself is the message!