This is a page listing various resources dealing with Bulgarian history, geography and related topics and subjects. Resources range from website and online article links to lists of recommended non-fiction bibliography.
FEEFHS Map Room - 50 detailed maps of Germany, Austria-Hungary, Russia, the Balkans, and the Baltics from the 1882 Blackie and Sons atlas, all available at the site of the Federation of East European Family History Societies. The same site also includes a nice Genealogy Resource Directory.
The "Balkans" FAQ, courtesy of Marko et al
Photos of Bulgarian rail vehicles and rolling stock, courtesy of Phil Richards