Google Inc. (NASDAQ:GOOG) has launched an extensions option within the Google Wave Navigation menu.  As of right now, Google Wave is still an invite-only service.  The gallery of extensions is intended for users to discover tools that developers are making with APIs.  The gallery is a set of waves that contain extension installers. “As a tip, you can also use the waves in the gallery to share a direct link to your extension’s installer with other Google Wave users — simply open the installer and copy-and-paste the URL (note: the panel arrangement and search query are included in the URL, but can easily be edited out),” stated Google Wave Product Manager Dan Peterson.  [Google Wave Developer Blog]