While I have used this module myself; one thing I am always on the look out for is creative uses of the GeoTools library for this blog; and this week on the user list I was pointed in the direction of OpenTripPlanner.
Thanks to Nicholas from the user list for the pointer; Nicholas is a contributor the Open Trip Planner project.
Now before you get too excited; just as with PGRouting; the ability to go from point A to point B (with a few waypoints along the way) is really dependent on the quality of your data and how much information you have about the intersections (turn directions and so forth).
Check out the links to both OpenTripPlanner and the GeoTools graph module; perhaps you can use a bit of direction in your next Java project.
Update: After hunting in the internals it looks like OpenTripPlanner has there own implementation of graph functionality and are using GeoTools for data access.