Using the Data View web part and the concept of an XML Data Island, I was able to get the Mindjet HTML Viewer control to render data directly from a SharePoint list.
See the demo here http://www.wssdemo.com/Pages/MindManager2.aspx (this will download the active viewer automatically).
The tricky part was grouping the list data to create the sub-topics. The XML format is very order specific and not well documented. I only have the evaluation copy of MindManager which doesn't have all the features.
