The recently released FREE WordPress plugin is called Admin UI Simplificator. (Note: UI is User Interface).
It is intended to be used by developers and designers who manage WordPress on behalf of their clients.
After the developer/designer activates the plugin other users will start seeing a very *clean* administration area.
That way clients will only see posts, pages and media library. They don't need to know or anything about plugins, themes, available updates etc.
The plugin simplifies the WordPress admin user interface by hiding most of the WordPress menus.
This doesn't mean that the functionality is not accessible. It is just hidden. Also the links on the admin navigation bar have been reduced.
Future versions of the plugin may include an option to allow users to switch from and to and the simple mode.
How to use it
Install and Activate the Plugin
Create a separate account for your client
The client logs in and sees clean admin area
Product Page of the Plugin.