In our company we do a lot small internal projects (not for customers).  We don't want to create for each project a team project.  Otherwise we come directly to the limitation of 256 Team Projects.

So we have created one Team Project with the name of our company.  In here we create for each small project we create an area.  Our policy is that everyone who has access to the team project, have read rights to all area's and contribution rights to the area project his currently working on.  Here's a little guide on how to set the correct rights.

1. Create a local TFS group.  We give it the same name as the area.
2. Add the users to this group who need contributor rights.
3. Add this group to the contributor group of your team project.
4. Go to areas and iterations
5. For the main area gave the contributor group view rights.
6. Add the new area
7. Add the group to the corresponding area with following rights
1. Edit Work Items in this node
2. View this node
3. View work items in this node
8. Go back to source control
9. Click for the properties of the team project.
10. Give the contributors read rights
11. Create a subdirectory for the area
12. Go to your area and click for the properties
13. Add the corresponding TFS group
14. Give following rights for this group
1. Read
2. Check Out
3. Check In
4. Label
5. Lock

Now you have your security correct when working with area's.