j-extreme  
   Free J/Carnac and J/View3D; INT's Java 2D and Java 3D graphics toolkits. [Freeware]
   http://j-extreme.int.com/

JInsight.com  
   Offers various class libraries including "JetChart Library", which displays a variety of types of charts. [Commercial]
   http://www.jinsight.com/

ILOG JViews  
   Library and components based on Java2D for maps, diagrams, graph layout, gantt chart, charts, editors and workflow. For client or server side graphics, including SVG.
   http://www.ilog.com/products/jviews/

JIU - Java Imaging Utilities  
   This library offers functionality to load, analyze, process and save pixel images. [Open Source, GPL]
   http://jiu.sourceforge.net/

Zooki Technologies  
   ExplicitLayout layout manager (Commercial) and EventInitializer to replace your anonymous inner classes (BSD).
   http://www.zookitec.com/

PJA Toolkit  
   For generating images on servers, without the need for an X server. [Open Source, GPL]
   http://www.eteks.com/pja/en/

JGo graphical object editor  
   A library for graphs, diagrams and networks, with an option for automatic layout by Northwoods Software. [Commercial]
   http://www.nwoods.com/go/jgo.htm

Java-Gnome  
   Java GTK+ and Gnome bindings using JNI. [Open Source, LGPL]
   http://java-gnome.sourceforge.net/

OpenJGraph  
   Various graph-drawing and traversal algorithms. Support for user interaction such as adding and removing vertices. [Open Source, GPL]
   http://openjgraph.sourceforge.net/

XColor  
   Subclass of java.awt.Color that knows 752 colors by name - can be substituted for wherever java.awt.Color is used in programs. [Freeware]
   http://www.darwinsys.com/freeware/XColor.jar

GEF - Graph Editing Framework  
   Class library for constructing graph/diagram editing applications. [Open Source, Apache]
   http://gef.tigris.org/

Java Vision Toolkit (JVT)  
   Library for machine vision and image processing applications [Open source, GPL].
   http://figment.csee.usf.edu/~mpowell/jvt/

Image Toolz  
   Manipulation methods for inversion, rotation, shifting, adding, loading, saving and creating images. (Open Source)
   http://www.bluering.nl/imagetoolz/index.html

Mica 2D Toolkit  
   A object-oriented 2D graphics library written in Java. [Open source, Software Farm license]
   http://www.swfm.com/mica.htm

Java Imaging and Graphics Library  
   Provides classes for data storage, image processing, image I/O and image display [Open Source, GPL].
   http://rivit.cs.byu.edu/jigl/v1_5/index.htm

Java Image Visualization  
   Applets, beans and applications. [Freeware]
   http://my.execpc.com/~larryhr/viewer/imageviewer.html

JLOOX  
   JLOOX Visualization Suite is a powerful set of components and tools for the development of high quality Java-based visualization applications. JLOOXTelecom is a distributable component set that includes easy-to-use network oriented graphical views and non
   http://www.engenuitytech.com/jloox/

HyperGraph  
   A Swing based API to visualise graphs using hyperbolic geometry (hyperbolic trees). Example applet povided. [Open source, GPL]
   http://hypergraph.sourceforge.net/

GINY (Graph INterface librarY)  
   Implements a very innovative system for sub-graphing and allows for stunning visuals and it provide a number of layout algorithms. [Open source, LGPL]
   http://csbi.sourceforge.net/

G  
   Generic 2D graphics library for Java. [Open source, LGPL]
   http://geosoft.no/graphics/

JGraph  
   Graph visualization component for Swing. Includes tutorial, FAQ, and user guide. [Open Source, LGPL]
   http://www.jgraph.com/

JDrawing  
   A Swing component for displaying vector graphics and animation. It can deal efficiently with very large vector images e.g. geographic maps or electronic circuits.
   http://jdrawing.sourceforge.net/

VirtualMachine.com  
   Utility class libraries: VMMemoryWatcher library that visually track memory changes in Java Virtual Machine; Flow monitor library that visually track process flow between containers. [Open source]
   http://www.virtualmachine.com/java/