[Pathfinder Adventure Path #32: Rivers Run Red (Kingmaker 2 of 6)][1] is largely compatible with 3.5 and contains:

> Expansive new rules for running your own cities and nations, by James
> Jacobs.

These are going to be expanded upon in [Ultimate Campaign][2], a recently announced 2013 source book which will contain rules for:

> building strongholds, attracting followers, and conquering kingdoms through warfare or guile…

  [1]: http://paizo.com/products/btpy8dml?Pathfinder-Adventure-Path-32-Rivers-Run-Red
  [2]: http://pathfinderwiki.com/wiki/Ultimate_Campaign