<extension
          id="navigator-viewbinding"
          point="org.eclipse.ui.navigator.viewer">
       <viewerContentBinding
             viewerId="org.eclipse.ui.navigator.ProjectExplorer">
          <includes>
             <contentExtension
                   pattern="<plugin_name>.myResourceContent">
             </contentExtension>
          </includes>
       </viewerContentBinding>
    </extension>

<extension
         id="navigator-content"
         point="org.eclipse.ui.navigator.navigatorContent">
      <navigatorContent
            activeByDefault="true"
            contentProvider="MyNavigatorContentProvider"
            icon="icon.gif"
            id="myResourceContent"
            labelProvider="MyNavigatorLabelProvider"
            name="Some Name"
            priority="normal">
         <triggerPoints>
            <or>
               <and>
                  <instanceof
                        value="org.eclipse.core.resources.IFile">
                  </instanceof>
                  <test
                        property="org.eclipse.core.resources.extension"
                        value="mpe">
                  </test>
               </and>
            </or>
         </triggerPoints>
         <possibleChildren>
            <or>
               <instanceof
                     value="<Class name of possible children>">
               </instanceof>
            </or>
         </possibleChildren>
   </extension>