For his map-based visualization, Tatsu Johnson wanted to show which colleges the current NBA team members originated from. He plotted the locations of each team with a pin in the team colors. Schools are plotted as black dots. He then drew a line between the school and team of each player. The brilliance of his design is that he applied transparency gradients to the lines so that they are more opaque at their origin and end points. This keeps the map very readable. If multiple players from a college ended up on the same team, the line between becomes darker.
Below the full map, he enlarged the areas around the three colleges that supplied the most players.
Tatsu revisited the map for his final, interactive visualization, providing a menu of teams and allowing the viewer to turn them on and off. In this way, you could, for example, compare the Chicago Bulls to the Boston Celtics.
Or perhaps you just want to see the Southeast Division.
There are any number of directions he could go with this to improve its utility. It would be useful to be able to filter by school as well as team, for example. Labels would be a useful layer, and it might be interesting to include movement of players between teams.