Packages for network analysis, simulation, and visualization
Graph Commons: just found this one recently; check it out.
gephi: very popular tool for network science
Ucinet: one of the standard SNA packages, along with Pajek.
SocNetV: easy to use, but a bit buggy last I checked. Will run a "spider" mapping a portion of the web.
NetworkX: a Python package for network analysis (requires programming)
Network Analysis and Visualization with R and igraph (requires programming)
ORA, a tool for Dynamic Network Analysis and network visualization. Kathleen M. Carley, 2014, ORA: A Toolkit for Dynamic Network Analysis and Visualization, In Reda Alhajj and Jon Rokne (Eds.) Encyclopedia of Social Network Analysis and Mining, Springer.
Meerkat: developed by our own CS folks; runs in Java
SEMOSS, an RDF-based open source context-aware analytics tool written in Java, leveraging the SPARQL
webweb, to display interactive networks in a browser.
See also Network simulations