I wanted to try out graph databases and Spring 3's REST support to provide a nice web interface to editing a graph structure.
Unlike most of my work there isn't a great deal of tests. The tests included are for experimental discovery purposes. I used maven's jetty plugin to drive most of the development.
The code here is by no means production ready.
HTML5 Canvas. It's suprising simple to build a nice looking dynamic page using the canvas API.
arbor.js "is a graph visualization library", you can even enable "gravity" and allow nodes to fall into place. Try dragging nodes around and let them settle.
Neo4j is a super fast, transactional graph database. The searching facilities are built on top of lucene which allows you to easily and quickly search and navigate the graph structure.