Following is a list of clubs. Mostly British members, but a fair distribution world-wide as well. This organisation coordinates doctors and clinics in over 125 countries. They provide members with detailed medical information and a directory of english speaking medical centres worldwide.
Membership is free but a donation is requested.
They issue a quarterly magazine. There is a lengthy charter in the rec.travel FAQ archive under the title 'South American Explorers Club Information'. The Great Expeditions Travelers Network is managed by the magazine of the same name. Find their entry in the journals summary. National Hobo Association - Yes, Hobo's have a club.