In 2013 the Double Seventh Festival, sometimes called Chinese Valentine's Day, is observed on August 13th. Girls pray to Zhi Nu for sewing skills (and a chance at romance).
Left-Handers Day dates back to 1992, founded by the Left-Handers Club. Enjoy your day, lefties, and be happy you live in a time when left-handers aren't forced to convert.
August 13th is National Filet Mignon Day. This has to be one of the best foodie days ever created, unless you're a vegetarian.