I've been toiling away on developing a campaign and I've been pillaging blogs and my gaming shelf for ideas and short cuts to alleviate some of the work load. I have a campaign influence list above of some of the posts from other blogs I've really liked and plan to use. I've also used (using) a batch of books OSRians and others have written.
My question today is, when developing a campaign what book do you use most? Are there a certain series you use? A single book that does for you. Is it a gaming or historical book?
When I am looking for cultural nuances to put into play I'll grab some anthropology books/articles and get ideas. GURPS books are great for boiling down a culture into gamable and interesting parts. For classes and rules I have a batch of retro clones I like to take from. The frame system is Swords and Wizardry Complete, but with a lot of Adventures Dark & Deep and Blood and Treasure tasted on. Not to mention a lot of my own concoctions.
So when you sit down to write up a campaign, what books are on the desk with you?