Ah, good times. This reminds me of a college project back in 1995! We created around 10 java applets illustrating Dijkstra, Kruskal, Prim and other well-known graph algorithms. For anyone interested in such illustrations take a look at: http://students.ceid.upatras.gr/~papagel/english/java_docs/j...
(and please bare in mind that these were created 16 years ago :))