If you're in Paris, today is the day to visit Pierre Hermé and grab some free macarons, along with help raise money to treat rare diseases. (And if you don't live in Paris, don't even try to find anything as good as Pierre's macarons; you will fail.)
To celebrate the third-annual Macaron Day, Pierre Hermé shops are offering three free macarons plus a special raspberry chocolate macaron to raise money for Fédération des Maladies Orphelines (an organization dedicated to treating rare diseases). To donate money to the organization, buy one or more red macarons. I recommend shooting for "more"—besides that it's for a charitable cause, any excuse to eat lots of macarons sounds good to me.