We currently run the look of multiple forums with one member list. Our site uses one WWF database with the different "forums" as categories. With a little modding, I set it up so that based on the URL lowcountrycops.com vs. palmettocops.com it knows which categories to show.
If one of my visitors goes to lowcountrycops, he only sees the counties which are in that disctrict of south carolina. The same for peedeecops.com, upstatecops.com and midlandscops.com. However, if he goes to palmettocops.com, he can see the entire state.
All I did was mod the SQL statement with a WHERE clause that filtered out the unwanted categories.
I hope this makes sense. I have not had much sleep lately.