You can create a sub site for various categories. For example:
* Departments - finance, marketing, IT
* Products - electrical, mechanical, hydraulics
* Projects - Trey Research, Department of Transportation, FDA
* Team - Retention team, BPR team
* Clients - new clients, old clients
* Suppliers - Supplier 1, Supplier 2, Supplier 3
* Customers - Customer A, Customer B, Customer C
* Real estate - property A, property B
The URLs for each will be, for example:
* http://yoursitename.wss.bcentral.com/finance
* http://yoursitename.wss.bcentral.com/marketing
You can keep track of permissions for each team separately so that access is restricted while maintaining global access to the parent site.