Dashboard Widget for Outlook:Mac2011 tasks
I have not found one.  While I might prefer a widget, there is the "My Day" feature of Office 2011 for Mac, whose hide/show hotkey is Ctrl-M by default.  This will open an Agenda-like window for the day, with a snapshot of your calendar events for the day, as well as a short list of Outlook tasks.  What is shown is, of course, mildly configurable for both Outlook and local content.