When I am casting about for ideas, I like to sort through the local train shop's back issues section. They have MR, RMC, and other good magazines from the 1950's to the 2000's (sometimes even ones that are only a few months old). Most are $0.50 each, so you can get a whole year's worth for less than the price of the current issue. Best years for MR is 1980's and 1990's, in my opinion.
Many of the Kalmbach books are simply reprints of articles from old issues of the mag itself. The only think to remember is that the DCC info (if any) will be out of date!
As for the Internet, The Gauge is one of the best (if I do say so myself
). There are some other good resources though. Do a search for "links" or look for resources - some of the forums have specific links highlighted.
Welcome to The Gauge!
Andrew