Images of Nature - Galleries and stock photography by Thomas Mangelsen. I love his work. Imagesite - worldwide photographer's directory. James Kay - adventure sports photos and new views of the American West. Lois Greenfield - beautiful work, of dancers and others defying gravity.
Meta links list - a UK source with a superb set of links.
Photography Happenings - good link list, from Singapore. Photography websites - good list. The Photo Page - claims over 800 links, well organized. WWW Photography links - University of Kentucky. Weak site American Photo magazine - site of the magazine, with lots of depth.