http://www.amadan.org/Innomine.htm
This is really the only page I've actually pulled things from whole-cloth. There are other pages from which I get inspiration certainly (particularly in my current work to get write-ups for the Dead & MIA Superiors), but this is the only one where I've literally printed stuff off and placed them inside In Nomine books for myself & players to use (I have the Dark Malakim rules sitting in the back of "Fall of the Malakim" for example).
If you are asking about non-IN resources that are still usefull in IN games, then nothing will ever top pantheon.org ... especially for any game involving the Old Gods.