As someone already said, Mike Bostock has a great design sense. But more importantly, he has built up a massive set of ready-to-use visualizations. Most others,

As someone already said, Mike Bostock has a great design sense. But more importantly, he has built up a massive set of ready-to-use visualizations. Most others, like me, use his examples as a base to build our visualizations. We often reuse the same properties used in the examples. For example, most circles have a contour of steelblue with a stoke width of 1.5 pixels, text nodes are all sans-serif of 10 pixels, all paths (lines between nodes) are colored #ccc with a stroke width of 1.5 pixels. These are pretty good defaults.