Thanks to Zenoss Developer Chet Luther for checking in a couple of ZenPack examples in the Example Techniques ZenPack.  The source is in the http://zenpacks.zenoss.org repository and provides the following examples:

• Adding a new top-level object to the DMD (Device Management Database)
• Adding a new property to an existing object type
  
• Adding a custom graph report
  
• Adding a new tab to all device
• Extending the Device object and creating your own type of components