Hallmark is offering a free 5x7 Mother's Day card using the code CARD4MOM at checkout. You must register for an account first in order for the code to work.

It looks like most of the free cards retail for 3.49. It doesn't include the more expensive cards, like the ones with sound, but I was able to get a free photo card with the code, so I'd suggest trying the code with different cards to see which ones will be free.

Click here.