The following list of links point to web-based resources for organizations that provide some level of information / insight helpful in conducting research into Swiss philatelic matters.

American Philatelic Society, 
American Philatelic Research Library

Arbeitsgemeinschaft Schweiz
Helvetia Philatelic Society (Great Britain)
Museum of Philatelic History (London)
Swiss Postal Stationery Collectors Club
Swiss Post
Union of Swiss Philatelic Societies

Liechtenstudy – looks like a stale link.

Swiss American Chamber of Commerce – Swiss Economic, Geographic and Social Data
United Nations Philatelists, Inc.