This link collection is yet quiet incomplete, and there are lots more sites worth occuring here. Yet I concentrated on those sites containing plenty of links themselves, so you can click your way through, and those sites rarely mentioned, hidden gems, and so on...
All of this will be improved by time, as I guess there are yet lots of great sites I myself don't know of. Hints and tips by mail are of course always appreciated.
Photos from Iceland
Icelandic photos by Rafn Hafnfjörð
It says "Since 1955 Rafn Hafnfjörð has been systematically photographing Iceland for the purpose of promoting the country. His photographs have been published in travel brochures, on postcards, calendars and web pages". And there are really lots good pictures on his site!
Collection of I don't know how many thousands of great pictures from Iceland. Several great Photographers have been contributing.
Landscapes of Iceland
Photos from all over the country and also pictures from the 19th century. Used to have collection of links to tons of great pictures from Iceland, which unfortunally is no longer available.
German forum to show and discuss photography. With photos not only from Iceland, but a separate section somewhere.