If you're great at writing or art, you might be able to earn some money creating graphics and/or prose for greeting cards. This page has a huge list of 47 companies that are regularly seeking submissions from freelance writers and artists for the greeting cards they sell.
Did you know writing greeting cards is a real profession -- and pays an average of $50K? Here’s which Hallmark jobs are available, plus a few other opportunities. - The Penny Hoarder http://www.thepennyhoarder.com/get-paid-to-write-greeting-cards/