Gephi: https://gephi.org

igraph: http://igraph.sourceforge.net

NetworkX: http://networkx.github.io

NodeXL: http://nodexl.codeplex.com

Pajek: http://pajek.imfm.si/doku.php?id=pajek

PNet: http://sna.unimelb.edu.au

Python Flickr API kit: http://stuvel.eu/flickrapi

Social Network Importer for Facebook networks: http://socialnetimporter.codeplex.com

Statnet: http://statnet.csde.washington.edu

Tweepy Python library for Twitter API: http://tweepy.github.io

UCInet: https://sites.google.com/site/ucinetsoftware/home

VOSON hyperlink network collection and analysis: http://voson.anu.edu.au