Great question!  This is on our product roadmap and as widgets mature they will become easier to use, configure and more robust.  Until we get there, advanced technical users can achieve the same results by using javascript and classes.  Business users can contract IGLOO services to build these for you - contact sales@igloosoftware.com for more information.

For the technical crew:
Build the HTML widget (appearance and content),
Assign a class to the widget in the Appearance tab,
Style at this time if applicable via CSS
Grab HTML content and put in custom javascript file
Since our platform has mootools, target the class and insert the HTML
You can now re-use that class on an HTML widget on any page to pull in the same content by dragging an empty HTML widget onto a page, and simply assigning the class in the appearance tab.

I hope this was helpful!