[@anointed Participant 15 years, 1 month ago]

I would probably start by finding a good heat map plugin which creates a widget for output. I would then modify the plugin to use topic_tags instead of post_tags. Then it would be a matter of placing the widget into a sidebar and your good to go.

*I am not currently aware of a heat map for bbpress, but modifying one for blog post topics should be just a matter of changing a few lines of code.