Paraphrasing the website:
  Gato - the Graph Animation Toolbox - is software [toolkit] which visualizes
  algorithms on graphs.
  - Graphs are mathematical objects consisting of vertices, and edges
    connecting pairs of vertices.
  - Algorithms might find a shortest path - the fastest route - or a minimal
    spanning tree or solve one of other interesting problems on graphs:
    maximal-flow, weighted and non-weighted matching and min-cost flow.
  - Visualisation means linking cause - the statements of an algorithm -
    immediately to an effect - changes to the graph the algorithm has as its
    input - by terms of blinking, changing colors and other visual effects.

WWW: http://gato.sourceforge.net/