National Puzzle Day is celebrated each year on January 29th. It's not an official national holiday, but The Griddle tries to celebrate it each year by giving away some nice stuff, telling people on Facebook, and by posting a ton of nice free puzzles to solve!
Not sure what to do for the day? You could celebrate by challenging your friends to sudoku solving time trials, print out some of my free puzzles to use in classes as handouts, get puzzle game iPhone apps, enter puzzle solving contests, and more!
Crossword Puzzle Day is celebrated each year on July 21st. It's not an official holiday either, but The Griddle has plenty of crossword puzzles and crossword variants to spice up your Crossword Puzzle Day!