Help Designing a Multi-Community Site

[BlueNinjaGo]

This is what I would do, but I don't know if it'd be exactly what you're looking to do.

Let's say you're looking to have 3 different communities.

Board A - Global
Board B - Community 1
Board C - Community 2
Board D - Community 3

Create 3 joinable usergroups. Usergroup 1-3.

Set Board A to be able to be seen by everyone.
Set Board B to only be seen if you're in group 1.
Set Board C to only be seen if you're in group 2.
Set Board D to only be seen if you're in group 3.

I'm not sure, but I would think that's pretty close to what you're looking for...