You know what would be awesome?
If someone invented a greeting card that had the postage already affixed to the envelope you get with it. Think about it. Stock up on cards, pull one out when you need it, address it, and boom. Drop it in the mail.
No more scrabbling around trying to find your stamps. No more realizing you're out. No more sending the card out late because it took you four days to remember to buy more.
Postage already on the envelope. Why can't someone invent that?