www.wiringdcc.com is also a good one.
Tony's trains is a helpful site as mentioned above, I also found the TCS site helpful, lists most manufacturers locos and installation examples, the link is for HO scale which I assume you are referring to but they also have N & O scale pages.
http://www.tcsdcc.com/Installation_list_by_Manufacter.htm
Jeff But it's a dry heat!