I am active participant as both a 'chaser' and an 'activator' in the Summits on the Air (SOTA) program.  SOTA is a great way to combine amateur radio and the great outdoors.  Activators are requred to hike to qualified mountain summits and make contacts while operating portable.  Chasers are the people you make contacts with while on a summit, whether they are at home in the shack, operating portable themselves or best yet, an activator on another summit.