Novo Card Publishers uses greeting cards for many different occasions. They are open to a wide style of cards, but recommend that you avoid sending in ideas that focus on current fads or a too-specific slice of society (be it cultural, social, or otherwise). They also suggest avoiding rude or obscene verse or prose. Payment rates are not specified.
In addition to accepting individual card ideas, Novo will also consider ideas for whole lines of humorous greeting cards. Check out the section titled "Humorous Card Lines."