MoodleFN

The Navigation block has a lot of features, but I find it can be a little overwhelming for students. If you would like to hide it from students, you can do so via the "permissions" setting for this block (or any other block). Just click on the permission icon and remove Student, Guest and Authenticated User from the "View Block" section. Make sure to leave the Teacher and/or Course manager roles intact.

Here's a screencast showing these steps: http://screencast.com/t/EVzFVMdhc

/Fernando