Yes, September 24th is National Punctuation Day. Chase's Calendar of Events bills it as "A celebration of the lowly comma, correctly used quotes, and other proper uses of periods, semicolons, and the ever-mysterious ellipsis."
And they should be celebrated! Punctuation marks are so misused and abused by the general public--especially the dear, misunderstood apostrophe--that perhaps this celebration will inspire a thirst for knowledge and proper usage. Okay, well, probably not. It's more just a chance for nerds like me to find solidarity with other nerds, such as those who form the Apostrophe Protection Society. (Let me tell you, just reading their manifesto got me fired up!)
Not sure how to celebrate? About.com's Grammar & Punctuation blogger Richard Nordquist suggests 10 Ways to Celebrate National Punctuation Day. Read, and then get busy!