I have done this slightly differently to JurgenG by setting up a new user group called VM and assigning it to the special user access level. I then turned off the components, extensions, articles, categories etc.. so that the main menu is then also most emtpy.
I then made a small modification to the quickicons module to show the VM2 links that I wanted users to have access to (Manage products, orders & users) although this can be altered depending upon your needs!
The result is that when our staff sign in they can only get to VM but when I log in I get all menus and full access!
See the screenshots (I have changed the normal icons to something which ties in better with Joomla 2.5 but you can use which ever ones you like!)
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