The internet offers many excellent resources for finding out more about Fritz Haber and Germany during World War I. Here are some samples.

"Master Mind" by Daniel Charles
An newly published biography on the life of Fritz Haber. "[A] thorough, sensitive, beautifully written account…. It is hard to imagine a more insightful portrait of Haber" (The Washington Times).
"Einstein's Gift" by Vern Thiessen
Winner of Canada's Governor General's Award, Vern Thiessen's gripping new play explores the moral crisis faced by Fritz Haber and Albert Einstein as their great discoveries launch the age of chemical and nuclear warfare.
NPR Report — The Tragedy of Fritz Haber
An informative and moving radio story on Fritz Haber's life and accomplishments.
The Nobel E-Museum
A biography of Fritz Haber provided by the Nobel Foundation's online museum.
The Chemical Heritage Foundation
A short biography of Haber, focusing on his achievements in chemistry.
The Significance of Fritz Haber
An article reprinted from a 1947 issue of "American Scientist," written by Morris Goran, the author of the only biography of Haber written in English.
Clara Immerwahr
It is very difficult to find information on Haber's wife in English. This is a site written in German, but sites like Google provide free translation services that will enable you to read it.
Weapons of War: Poison Gas
An excellent history of the use of chemical weapons in World War I; part of a larger site containing a wealth of information on the war.
Trenches on the Web
Another great site filled with interesting information about World War I, including many cultural items such as posters, popular songs, and phrases coined during the era.
Propaganda Postcards of the Great War
A site filled with propaganda images created during World War I.
Music from the Great War
Patriotic songs and marches composed during the first World War. Enter "music" in the search box at left when you get to the main page.