American Rhododendron Society: This is the main (international, despite its name) rhododendron organization. The site provides lots of information on rhododendrons and their care, on sources of rhododendrons, data about individual species and hybrids, access to a seed exchange, and a searchable database of pictures of both species and hybrid rhododendrons.
Rhododendron Species Foundation: This is the home site for the Rhododendron Species Foundation and Botanical Garden in Federal Way, Washington.
Western North America Rhododendron Species Project |
Vireya.net - Vireya Rhododendrons |
Danish Chapter of the ARS |
RHS Rhododendron, Camellia and Magnolia Group |