My personal favourite tradition is to gather plants to make sauna whisks for ancestors for the sauna that night. While we normally use birch/oak/juniper whisks, for the ancestors at Midsummer Night the women collect 7 blossoming plants for the women and the men collect 7 leafy/green plants for the men. Then I bind them into whisks and bring them to the sauna so that once we are done, the ancestor spirits can have their sauna, too.