Viabella

 Viabella purchases art and verse for use on greeting cards. Their writers' and artists' guidelines are refreshingly straightforward.

Submissions must be made through their art or verse web forms. (Links are at the bottom of the guidelines page.) Don't submit more than once a month. Payment for accepted verse ranges from $50 to $100, with humor generally getting a higher payout.

One nice thing about Viabella is that they only use purchased material on greeting cards and stationery items, so writers and artists "are free to sell your accepted submission to others outside of this industry."

Check out Viabella's online store for an idea of the type of cards they sell.