For a pet project of mine, I'd like to visually render the concept of "flow" through a "network" (a graph with weighted edges). Is there something out there that already allows me to do this? It can be absolutely rudimentary. I can provide all the data (when to transfer a "dot" from one node to another, etc.) and I want it to generate an animation of the system for me.

Is such a thing available, open source, out there? I can probably just build it from scratch, or using some unrelated pieces, but I'm sure I'm not the first person to want to.