My Sources

It just occurred to me that my resources for Pathfinder are a bit more extensive than some GMs might have. (I got probably something like 80%+ of the campaign setting books.

I currently use:

1.Pathfinder Core

2. Bestiary 1 & 2, as well as the bonus bestiary from the Paizo site

3. Advanced Player's Guide

4. Ultimate Magic

5. Player's Guides for: Rise of the Runelords, Curse of the Crimson Throne, Council of Theives, Kingmaker, Serpent's Skull, Carrion Crown (All free btw)

6. Pathfinder Chronicles: Guide to the River Kingdoms, Cities of Golarion, City of Strangers, Classic Treasures Revisited, Faction Guide, NPC Guide, Seekers of Secrets, Gazetteer, Guide to Korvosa, Classic Monsters Revisited

7. Pathfinder Campaign Setting: Inner Sea World Guide, Lost Cities of Golarion, Rule of Fear

8. Pathfinder Companion: Adventurer's Armory, Andoran: Spirit of Liberty, Cheliax: Empire of Devils, Dwarves of Golarion, Gnomes of Golarion, Qadira, Halflings of Golarion, Inner Sea Primer, Orcs of Golarion, Faiths of Purity.

This doesn't include things like the Iconic downloads or any of the various beta tests they put on their site. Or the Pathfinder SRD or Golarion Wiki.