Birthday (and other) cards can really add up, so my strategy is to make my own! Michaels and Hobby Lobby carry packages of 50 blank cards for $10, and they often have 50% off any item coupons, making the cards themselves $0.10. I then print (either by computer or by hand) a message on the inside, and attach a picture. Sometimes I use a picture of the recipient, or a fun picture of my own kids.
For example, I've used this picture of Henry (from his 3rd birthday) with "Happy Birthday Partner!" for birthday cards:
Or this one for a new baby, with "congrats on your newest bundle of joy":
Or for "showers of blessings":
For thank you cards (especially from the kids) I take a picture of them with the giver or of them playing with/using the gift.
Depending on where you get the photos developed, the pictures cost less than $0.20, bringing your cost per card to less than $0.30, about a tenth of the price of a card at the store!
So what Works for you? Please visit Shannon for more ideas!