This network graph shows common contributions between representatives in Congress:
A relationship exists between two elements in the visual if they share a relationship with at least one member of the other group. For instance, both Bernie Sanders and Sam Brownback received campaign contributions from the the National Association of Realtors.
Line thickness represents number of shared relationships; and color represents Democrat to Democrat, Republican to Republican, and cross-party connections. There's a zoomable version, but like a lot of network stuff it still feels cluttered. I'm sure some node interaction goodness would do this some good.