Celebrate by not looking surprised if someone says, "Happy National Grammar Day."
Other ways to celebrate:
* Impress a friend by using "whom" in a sentence.
* Annoy a stickler by not using "whom" in a sentence.
* Spread the word that there's no rule against ending sentences with prepositions or splitting infinitives.
* Spread the word that Strunk and White didn't understand passive voice.
* Tell a friend who believes "between you and me" is wrong that it's actually better than "between you and I."
* Brush up on one grammar term you either don't know or have forgotten, such as object complement, predicate nominative, or subjunctive.
* Start a sentence with "and."
* Warn a school kid or college kid that even educators can sometimes spread bad grammar advice and that he can always check facts in a good usage guide like Merriam-Webster's Dictionary of English Usage, Garner's Modern American Usage, or Fowler's.