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
35 WAYS TO MAKE MONEY THAT ACTUALLY WORK! (Updated for 2017)
35 ways to make money for teens (and adults) - Need to make some extra cash? These are some ideas that will work well for teens and many of them even for adults looking to make a little extra money on the side!
How Much You Should Have Saved in Your Retirement Account, by Age