London's UKType.com set up a call for entries for designers to "mix sexual innuendo with typography." The brief for this states that the entrant is supposed to design a card either for a typeface or letter of the alphabet - of course in the vein of that innuendo. There are a few other restrictions for entry that you can find on the Tart Card section of the site.
If you want to enter, the deadline is April 10, 2009. If you don't, and just want to peruse the entries as they come in, go to the site as well.
There will be an auction of these cards sometime in the future with proceeds benefitting the St. Bride Library in London. According to the site, St. Brides is "one of the world’s most important resources for the graphics industry." STEP says that St. Brides is a printing and graphic arts library. Sounds absolutely wonderful.
Just in time for Spring and all of the randy things that can happen, Tart Cards are the way to go. Oh, boy, I feel a scandal coming.