Simple drupal admin for clients?
Although Workbench is good I use to build a custom admin with:

admin menu and admin menu source to build a custom admin menu per editor.

Also is good to have menu per role to choose what menus can edit editors.

With views and views bulk operations you can build a better administration interfaces. 

With this you must built it, but I think you will get a better options that Workbench.

Also you can use dashboard to help user to see their options.