Desert USA -  Descriptions of plants, animals, geology; lots of desert articles, ancient and recent history.
Maturango Museum in Ridgecrest, CA - Upper Mojave Desert Information.
Desert Tortoise Preserve Committee
Darwin, California (near Death Valley)
Living Desert Zoo & Gardens (Palm Springs, California)
Center for Biological Diversity
Center for Biological Diversity's California Desert Conservation Area
Oregon Desert Trail Association
Basin and Range Watch
United States Bureau of Land Managment (BLM)
Glen Canyon Institute
Southern Utah Wilderness Alliance
Arizona-Sonora Desert Museum (Tucson, Arizona)
National Parks Service
National Parks and Conservation Association
Friends of Nevada Wilderness
Wilderness Society
Mojave National Preserve Conservancy
Sierra Club
Eastern Mojave Geology - A Botanist's View (Really nice field notes and photos)
Friends of the Inyos
Oregon Natural Desert Association
Wilderness Watch (monitors wilderness areas in western states)
Risking Too Far - Bob Davis' website (Writing and photos of desert hiking and camping)
Postholer.com/Colter - Buck Nelson's journal of his 2012 solo, Desert Trail through-hike