I hate throwing away the cute cards that I get, but I can't possibly keep them all. So this is what I do, I turn them into postcards and send them on to someone else.
Take a card that doesn't have writing on the back of the front of the card (the left side of the inside on side fold cards, and the top of the inside on top fold cards).
Open the card and cut right down the fold. You can use a paper cropper (like scrapbookers use) or just use scissors.
You now have 2 halves of the card. Dispose of the "back" of the card and you are ready to use the "front" of the card. Turn the picture side (or front side) over and address the card and write a short message. Use a post card stamp (which is cheaper than a letter stamp) to mail it.
It is a great way to upcycle (great for the environment), you should have a ready supply of 'free' cards on hand to give out at any moment, and it is cheaper to mail (even better for your budget).
I read all of the cards that I get and immediately get rid of the envelope (recycle or trash), cut the cards as demonstrated above, discard the portion that's not necessary, file away the cute 'front' and I have post cards at a moments notice.
Have you done anything like this? What do you do?