Set up a private area.
I have a section that contains documentation only our committee can see. If you go into the Help documentation and go to 'Standard Applications', 'Private Area' and click on the red 'Private Area' link you will find how to do this.
On logging in to your site, only those who have been given access to the private area will see the link in your menus.
Below is a clip from the Help pages.
'Private areas are commonly used to create a members only area of the site with exclusive content and interactive applications.
To enable and configure a private area, click the Content Management tab and select the Applications page. Next click the Add Private Area button and supply a name and URL stub for the private area. Once you have enabled the private area it will be added to the list of applications and clicking the Manage This Application link will display the standard administration interface. Within a private area the administration interface operates in the same way as the administration interface for your main site.'