Our local bike-to-work day is Friday May 18.
There will be free coffee and, um, "power rings" downtown along with a presentation by the city police bike patrol.

My small bike club has a May Commuter Challenge with a sponsor funding a prize if 3+ people participate.
The participants vote on a winner (other than themself), the sponsor votes in case of a tie.
The winner gets to pick a prize, can range from bikey stuff to the first round of adult beverages on a social ride.