Every year, I keep homework and other papers from the boys. I then try to go through it and find just the highlights of who they were, where they were, what they were doing, what they had trouble with, what they were good at, and bind it together in a little book.
This is my older son's preschool collection.
A few years ago, I stumbled over some primary school papers of my gramma, some crafts, a report card, and homework. It was completely facinating to think of her as a little girl, and to see her dad (my great-grampa's) signature on the report card. This inspired me to try and leave something similar behind for my children's grand children.