I have done some tests using the new Google Docs (Google Drive) integration in Alfresco 4.2. You can se all on how it works in this video created by Jeff Potts, Alfresco. The Alfresco engineers has all done a great job here, and I would love to use this as my primary way of editing office documents. If it were not for what the actual output of the advanced formatted documents look like.
If you are looking for plugins to Alfresco Share, Will Abson (personal blog) has created an excellent collection of dashlets, themes and document actions available at Share Extras. To this collection I have contributed a dashlet, Google Site News, the first version created soon after the release of the initial release of Alfresco Share. It has been available as part of the Alfresco Developer Toolbox downloadable from the Alfresco web site.