John Ericson's website HornMatters.com. Lots of online resources.
W. Peter Kurau
Mason Jones, another French horn player to whom I listened incessantly in college! Google Image Result for http://www.philadelphia-reflections.com/images/mason-jones.jpg
Philip Farkas (1914-1992)
Marvin C. Howe - biography and list of works. He was one of the 20th Century's greatest horn pedagogues. His book for beginners, /Method for the French Horn/, is quite possibly the best beginner method book to date. -SP