GUESS is Eytan Adar's (HP Labs) toolkit for doing graph exploration and visualization. GUESS is a combination of a custom Jython for querying graphs, JUNG for graph algorithms, and Piccolo, Prefuse, or Touchgraph for visualization. Not quite a Pajek or UCINET replacement but that's the long term goal. The big win is probably the embedded, domain specific, interactive language. And since Adar and his colleagues are working network analysts GUESS is being developed where the rubber meets the road.