GUESS is an exploratory data analysis and visualization tool for graphs and networks. The system contains a domain-specific embedded language called Gython (an extension of Python, or more specifically Jython) which supports the operators and syntactic sugar necessary for working on graph structures in an intuitive manner. An interactive interpreter binds the text that you type in the interpreter to the objects being visualized for more useful integration. GUESS also offers a visualization front end that supports the export of static images and dynamic movies.
Because GUESS is Jython/Java based you can also construct your own applications and applets without much coding. GUESS is distributed as GPL and makes use of a number of great open source packages and contributions. Feel free to explore the website and download the application or read on for more details.