Any object can be linked to another. You can link multi-selected objects to a parent.
Select child object(s) and press Link toolbar button. Now, you can directly click on parent object OR select it using SceneList.
Simple Example: Create two sphere meshes and link one to the other. Then, select 'parent' sphere and rotate it. Child sphere is rotated too.
Unlinking objects is pretty easy.Just select 'em and press Unlink toolbar button.
Currently(ver. <= 1.3.4) there's only one way to see if an object is linked. Use Properties dialog to see if there's a parent object.Menu/Edit/Properties (Ctrl+P). OR If the Unlink button is enabled(not grayed) then all or some of selected object are linked.