Bastille day commemorates the French Revolution, or more precisely the storming of the Bastille, which happened on this day back in 1789.
School may be out for the summer but the calendar often offers teachable moments. Here's a good overview of Bastille Day written for kids -- including just how insulting Marie Antoinette's famous words were. [Wanna learn more? Do some research through the Internet Archive.]
Why should we care? Well, the French Revolution gave the world restaurants (as opposed to dark, ale-filled inns), and provided the central plot elements for Charles Dickens' A Tale of Two Cities (the only Dickens book I have actually managed to read cover to cover without resorting to Coles Notes or similar crib sheets). [Ooh, here's an audio version too.]
And in case that was too much information, here's some Mel Brooks to take your mind off it all (be warned this is a PG-13 clip...):