Gephi is a tool for data analysts and scientists keen to explore and understand graphs. Like Photoshop™ but for graph data, the user interacts with the representation, manipulate the structures, shapes and colors to reveal hidden patterns.
HEURIST is an extremely flexible, end-user oriented, web-based data management system designed specifically for Humanities data. Developed since 2005, it has been in active use across many projects since 2009. It is available both as a free web service for researchers (hosted at the University of Sydney Data Centre) or for installation on a physical or virtual server (Open Source on gitHub).
According to its website, "VOSviewer is a software tool for constructing and visualizing bibliometric networks. These networks may for instance include journals, researchers, or individual publications, and they can be constructed based on citation, bibliographic coupling, co-citation, or co-authorship relations.