http://www.floraislands.is
This is the major internet site on the flora of Iceland. It has been set up by Hörður Kristinsson, the author of the classic field guide on Flowering Plants and Ferns of Iceland (see the bibliography section). The site is in Icelandic. However, non-Icelandic speakers can make use of the Latin name-list of the Icelandic flowering plants, ferns, mosses and lichens. Under each name is a link to a specific page (in Icelandic) with photo's and distribution maps.
http://www.icelandicforest.com/
This is the home page of the The Icelandic Forestry Association. The Icelandic Forestry Association was founded in 1930. It is a nationwide alliance of 61 local and regional forestry societies, with a combined membership of about 7500 people. The Association is a non-governmental organisation and is a major movement for nature conservation in Iceland.
http://www.nat.is/travelguideeng/flora_iceland.htm
This site describes in general terms the vegetation of Iceland.