maddman75 said:For general information on medieval warfare, castles, and seiges you can't beat the old 2e castle guide. You can get it from RPGNow for $4.95 here - http://www.rpgnow.com/product_info.php?manufacturers_id=4&products_id=958&
It has excellent chapters on medieval life, castles, chivalry, seiges, and all aspects of castle life. Its heavy on fluff, so the fact that its for AD&D isn't that big a deal.
philreed said:I'll second this one. Very useful and, in PDF, reasonably priced.