So it's something of a joke holiday, and a joke module. But the community point is serious. My company will be giving all our employees this day off to work on any issue(s) they like in the Drupal community, something we can afford. Joined together we'll do something.
I've implemented a bare bones module that creates a block with a picture of Dries in it. The block title changes to a special message on Driesday. It encourages the site's users to participate in Driesday.