Making intranet site

Hi All

I'm looking into the possibility of using Drupal for intranet.

I like to have this funktions.
Forum
User list
Download section. "for doc, and advertising stuff"
Only login site is visible until you login.
I need a funktion so i can assign i period of time a user is allowed to log in to the intranet. "like the artikel funktion publish/unpublish by date and time"

Are there any that can help me with this, what components to use and so on.

Solhaug