A friend-of-a-friend of Jason’s told him about this, and it’s a fantastic activity/memento for any paper/pen/calligraphy/stationery nerds. Basically, you buy a small book, called a shuinchou (朱印帳) usually for about ¥1000 (roughly $10). You take it with you to each shrine or temple you visit and there will be a place where, for ¥300, a monk will write calligraphy and then stamp it with the seal of the shrine. It’s incredibly beautiful – both watching them write it, and the resulting page of calligraphy and stamp.
Here are the seals I collected on this trip: