Walking Papers was a service that allowed you to print out an OSM map, annotate it, and scan your annotations back in so that you could add new features to OSM. The website embedded the Potlatch editor into its main page so you could edit directly after scanning in a printout. There was also a JOSM plugin.
In 2012 Field Papers was introduced as a continuation of the walking papers concept, with a new multi-page atlas feature, and a specially designed printable map style. Field papers largely supersedes Walking Papers.