If greeting card merchandising doesn't appeal to you, how about writing them? This sounds like very fun, interesting work to me because as we all know, greeting cards are very short and to the point. Usually you don't need to write more than three or four lines max. Almost all greeting card companies (with the exception of Hallmark who doesn't openly accept submissions) will consider work from freelancers.
Huge List of Companies That Need Writers & Artists For Greeting Cards
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.
from MoneyMakingMommy - An Everyday Guide to Work at Home
Greeting Card Jobs From Home - Writing, Illustration & More
Get in touch with your inner poet! Or how about finally sharing those illustrations or quirky drawings? Or maybe you just want a super flexible job that allows you to earn a paycheck and freedom. Check all the wonderful options that the greeting card business has to offer those that want to work from home being creative. Or those looking for a part-time, flexible position that lets them pretty much be their own boss. MoneyMakingMommy.com
Need Money? Here are 276+ websites to make extra money
If you need to make extra money, you HAVE to check out this list of hundreds of legit sites that will pay you. From market research to writing your own greeting cards, this page lists a ton of places and I bet you haven't heard of half of them!
Would you like to work at home as a freelance writer? Here are some of the various types of writing gigs (blog posts, recipes, short stories, greeting cards, etc.) where to find them, and how much they pay. via The Work at Home Woman