Yesterday I ran across the "Definitive Metal Family Tree" from the documentary "Metal: A Headbanger's Journey". The original chart is pretty compact and hard to follow the lines, so I had a go at reformatting it.

I dropped the data into a Graphviz file and tweaked the layout so it looked decent. The result is a chart that's much easier to read because all the genres are sorted mostly by timeline with clear inheritance arrows between them. Click on the image to view the readable full size one: