The Drupal menu system is very smart about when it shows menus. It knows when a user has access to the menu, based on the roles the user has, and ultimately, the permissions the user has.
This is a great feature of Drupal. However, you still need to provide some form of navigation. Out of the box, Drupal provides a Navigation menu and both Primary and Secondary links menus. No matter which one you choose to use, you can enhance this navigation by making it easy for users to get to where they want to go - or even better, help them find the content they may be interested in.
In this video, I discuss the use to two different modules in particular. Dynamic Persistent Menu and the Me modules.
The information I provide in this video can apply to many other navigation modules. It's the Me module which is providing the magic to make your users happy with accessing their content. You find information about the specifics of Dynamic Persistent Menu and creating a block based navigation area for your site. The advantage to block based navigation (as opposed to html/template based) is that an admin user, with the right permissions, can control the menu to their heart's content.
If you have more suggestions about cool navigation and menu modules then please leave them in the comments below.
Modules referenced in this video
Note: About the extra feature in Dynamic Persistent Menu. This is a link to the issue where I posted a patch that adds the checkbox feature of not showing submenus when the given url matches the menu which was selected.