Fred Fabro, Jon Husband and myself (part time only for me!) are working on this in the soon to be released beta of QuickDraft (or whatever Fred is calling it these days :-) !). The beta will be crude but hopefully show the potential of what we have in mind for future releases.
We are interested in a design that combines a search interface with a visual representation of blog conversations. We believe that a text-only representation of search results and blog linkages will hide the complexities of these conversations as well as conceal valuable data. Additionally, there will be opportunities for other features, such as dynamic filters, zooming, and so forth, pending early testing and prototypes. Who else is working on the visualization of weblogging conversations?