Dynasties & Demagogues by Atlas Games- this is an incredible resource for political games, and something often overlooked in D&D.
Crime & Punisment by Atlas Games- what Dynasties and Demagogues is for politics, Crime & Punishment is for law, law enforcement, and legal codes (both secular and religious).
Codex Arcanis by Paradigm Concepts- THE coolest and best written D&D setting out there, its more Romanesque than medieval, and is very well thought out and has room for lots of moral grey areas. The whole Arcanis line is incredible, especially the Player's Guide and Seethragore (the best representation of lizardfolk and yaun-ti I've seen).
The Foul Locales series by Mystic Eye Games is great too- I've gotten tons of use out of their adventure vignettes, and they are suitably dark and fairy-tale like for my tastes.