The British Art Medal Society (BAMS)
BAMS publishes a bi-annual magazine called The Medal which is a vital source of information about historical and contemporary works.
Art Nouveau medals - an introduction to Belgian and French medals 1870 onwards by an enthusiast. Not much detail yet but some nice pictures
This site run by Robert Kokoteilo has masses of further links to ancient coin dealers and chat rooms.
Royal Numismatic Society A highly academic society with many useful, erudite publications.www.rns.dircon.co.uk
Rich Hartzog A lively dealer in the USA for tokens and exonumia, mainly US focussed.
Oriental Numismatic Society