Everywhere and everything.
The world structure and basic concepts of how things aork are mine. The details and all the window dressing has probably been done a million times over.
I read a lot of homebrew websites and borrow thier ideas. Dragon magazine is a huge influence on me for inspiration.
Other soruces of inspiration, books, movies, the news, art.....
The major creative goal behind my world was to include every cool idea I have come across in a logical manor.
As a matter of fact when describing my world to new players I tell them I wanted the whole world to look and feel like the bar seen from Star Wars in Mos Esley.