I used Patricia C. Wrede's worldbuilder questions to flesh out my world after most of the design work was complete. Granted, I've worked on my world for roughly 20 years now, so I've had plenty of time to hammer things out. Wrede's worldbuilder helped me get a lot of the little nuances done.
You can find Wrede's worldbuilder topics at
http://larseighner.com/world_builder/index.html and
http://www.sfwa.org/2009/08/fantasy-worldbuilding-questions/
I prefer this second entry.
I also use http://www.io.com/~sjohn/demog.htm to work out population numbers.
Good luck in getting it worked out!