Graphviz is open source graph visualization software.  It has several main
graph layout programs.  It also has web and interactive graphical interfaces,
and auxiliary tools, libraries, and language bindings.

Graph visualization is a way of representing structural information as diagrams
of abstract graphs and networks.  Automatic graph drawing has many important
applications in software engineering, database and web design, networking, and
in visual interfaces for many other domains.

This requires SWIG for building language bindings (available at
SlackBuilds.org).