International Randonneuring Clubs and Organizations

Audax Club Parisien (Paris-Brest-Paris)
Audax Brasil
Audax UK
Randonneurs Mondiaux
Randonneurs USA

Events Web Sites

Edinburgh - London 1400
Gold Rush Randonnee 1200
Granite Anvil 1200
National 24-hour Challenge
Paris-Brest-Paris 1200

A few worthwhile links:

PBP History by BC Randonneurs
BC Randonneurs and PBP history

Brevets explained in Wikipedia
Brevets

Paris-Brest-Paris reference in Wikipedia
Paris-Brest-Paris

Randonneur reference in Wikipedia
Randonneurs