My dad is a pack rat and I have had one heck of a time sorting through all his stuff, but one of the interesting things he collected are postcards. He started sometime in the early 60s, when he starting traveling and requested his friends send them to him from their travels. In addition, he bought himself one at every single city or landmark that he visited, marking on the back the date of the visit and the reason (usually army or cricket outings). So with all those, I'm thinking I'm going to try making a timeline and tracking his explorations.
Of more interest, maybe, are the ones with actual notes from friends. It's fun to see who wrote him most often, as well as the style of language that was used. Anyways, when I get around to sorting through them, I'll post it here, but run it by him first. He can fill in the blanks for me.