What homebrew stuff is in your version of Golarion, whether it be arbitrary changes as GM or the consequences of PCs? It can be anything, no matter how major or minor it is.
Some of mine (not a complete list):
-the Rain of Stars occurred in Numeria 900 years ago as opposed to 9000 years.
-Taldor officially outlaws Sarenrae's faith, and they are not evil for doing so. Unofficially, the situation of Sarenrae's faith is a complex issue in the country despite the official stance on it.
-Anastasia Romanov is the new Queen of Irrisen, and Baba Yaga has promised to never return to Irrisen. (You can guess how this ended up happening.) The Linnorm Kings have not been blind to this...
-Dreamscarred Press's psionics are a direct result of the Dominion of the Black interacting with Golarion a long time ago in some way. It's essentially using your brain to "hack" reality, and the technique blurs the line between natural science and the supernatural.
-Androffa did not suffer an apocalypse at the hands of gods. It was instead reached by the Dominion. With what happened after, being destroyed by wrathful gods would be a mercy.
-Andoran has rather sour relations with most of the Inner Sea's big time powers (Taldor, Cheliax, Absalom, Osirion) with their overly zealous stance on slavery. As a result, any ship flying the Andoran flag is simply barred entry from all ports from these nations. In Absalom, this is almost as controversial as slavery itself.
-Aroden was (is?) a Veiled Master. What this means for Iomedae, Cayden Cailean and Norgober isn't known...yet.
Excuse me good Sir, but do you have a minute to talk about the 'Search' function of this messageboard?
Verily, I have not heard of the existence of such a thing even though it should have been quite obvious. Excuse me while I flog myself until I see stars from this most embarrassing situation.