We invite a bunch of the local teams to go paintballing with us (
https://www.facebook.com/events/508753419135382/). Its a good way to release some stress..
We also, like many other have movie nights. (chiefly because we will be doing robotics somewhere and person A will say a movie quote/reference that person B can complete but then person C doesn't understand it so person A and B and the whole rest of the team setup a movie night so that person C will understand the reference) We also hold a End-of-Season Pool Party in May where we turn what that years game was into the water game version. Last season before a Saturday morning build everyone got together at a member's house to eat breakfast.
We also sometimes attach leisure activities to some of our robotics events. For example, we were doing at the Boy Scouts Expo last summer in New Orleans City Park. Our part of the event ended around noon, so we spent the rest of the day playing in the park, climbing trees, walking tight ropes, watching ducks in the pond, etc. After demoing at our state capital three years ago we toured the (i believe) official Louisiana museum.