Implementations of various algorithms in Python and Java. For fun. Do I need to get out more?
Some Java classes that involve graphs (e.g. BinarySearchTree.java) have solutions to exercises from the Sedgwick "Algorithms" book.
They generate output in .dot format.
Run the following command to generate a pictorial graph PS image. which you can then open and view at your leisure:
dot -Tps graph.dot -o graph.ps
You'll need to install GraphViz first though.