Thomas Mangelsen is a superb nature and wildlife photographer who has published a number of books. Do a search for the Images of Nature gallery.
If you have an interest in railroading, especially the steam era, look for the photography of O. Winston Link.
Another good source of photography books is the National Geographic Society. They have published many books on all areas of photography.
One book I found particularly poignant, perhaps because I served there, was REQUIEM, By the Photographers Who Died in Vietnam and Indochina, edited by Horst Faas and Tim Page. The book is full of very powerful photography from the conflict in Southeast Asia and features biographies of the photographers killed during the war. There is also a video from the History Channel entitled "Suicide Missions: Combat Photographers" that parallels the book.