I made this git to be able to show a few of the d3 demos I'm working on as I learn.
Snow: Animated falling snow using image transparency and motion random transitions.
Random motion scatterplot: Scatterplot with random colors on mouseover, and random transitions (color, size, location) on click.
Force Layout: Multibody repulsion visualization showing repulsion from the mouse. Use the up and down arrow keys to increase/decrease the force (and change between attractive and repulsive forces). Click to change the color of the circles to a random rgb color. Based on this code.