hi mat,
nice to read there's more people interested in the combination of info
visualization and TW.
I'm still hoping for something like you describe above, but the other
way around:
have the tagmindmap (or any other visualization of content) as
screenfill/background and the tiddlers pop up next to the node that's
clicked on.
My try in implementing tagmindmap and moveablePanel is at
http://www.mobilelibrary.nl