Tandem Chess is a fun way to play team chess. Two (or more) people all play each side's pieces, but each person makes one move, then waits for everyone else on the team to also make a move before their next turn. The board may look completely different by the time you get back up to make a move!
There's no entry fee, and it's not rated - time control is G/10;d10 to allow you to think a bit on each move.
As always, there will be casual chess all night.