This is a music performance / sequencing application I'm writing called tiction. It will eventually be set up on a multi-touch table, but it works great with just the mouse and keyboard so far.
In this example, each node sends a MIDI note when triggered, the pitch and velocity of which is controlled by its current position on the screen. MIDI continuous controller messages can also be sent. One-way connections allow the next node(s) in the network to be triggered after a set number of tics. Connecting nodes in a closed circuit makes a repeating pattern.
Also, when an event is sent, some physical event occurs - this can be a slight pull toward other nodes, a slight push away from other nodes, or a jiggle in a random direction. Springs in the inter-node connections keep groups of nodes together amidst all this (ordered) chaos.
This early version is being written in Processing with proMIDI, traer.physics, and ControlP5.