I've got a box containing yuppy Moleskines, notebooks, notepads and cocktail napkins with descriptions of the adventure and random other detritus thrown in. The random bits - boarding passes, trail permits, wilderness permits, receipts from post adventure meals adds the extra bits that stimulate great memories each time I open it.
one of the coolest items to discover in the papers of my grandfather was my greatgrandfathers journal of a bicycle trip across Europe in 1911 - with pictures, including with Alpenstock on a glacier in Chamonix. It was simple looseleaf sheets, but quite amazing.