Gephi is a free, open source interactive visualization and data exploration tool. Users can manipulate the display to uncover new facets of the data, enabling intutive exploration.

NodeXL is a free, open source tool for generating and exploring network graphs from Microsoft Excel files. It is particularly suited to data from social media sources, and includes the ability to directly import data from Twitter, YouTube, Flickr and email, with additional plugins available for gathering data from Facebook, Microsoft Exchange, wikis and URLs. The tool generates visualizations that can be adjusted, zoomed and filtered, with additional features for vertex grouping, graphing metric calculations, and automating tasks. NodeXL can both import and export data in GraphML, Pajek, UCINet and matrix formats.

Siena (Simulation Investigation for Empirical Network Analysis) is a free program for statistical analysis developed particularly to work with social network data, but also applicable to other forms of network data. It models network dynamics via Markov chain models; this approach is best applied to data where relations between actors and their behaviour can be treated as a state rather than as an event. Siena's statistical analysis processes can be time-consuming, as the system works via computer simulation of the network. It was in continuous development from 2001 through 2010, releasing versions up to 3.2. Development on Siena as a stand-alone program has concuded, and the project has shifted focus to RSiena, a version of Siena deployed in R.

RSiena is a free, open source social network analysis package for R. It replaces Siena (Simulation Investigation for Empirical Network Analysis), which was a stand-alone program for Windows. Like its predecessor, RSiena is optimized for social network data, but is also applicable to other forms of network data, and relies on Markov chain models to generate network dynamics. This approach is best applied to data where relations between actors and their behaviour can be treated as a state rather than as an event. Users not familiar with R can run RSiena via the provided graphical user interface.

It is highly interactive and allows a researcher to extend their work from a dedicated graph analysis package such as Gephi and share it via the web to allow for communication of research outputs, while permitting viewers to explore and discover their own findings from the raw graph network.

SylvaDB is a graph database management system. It allows users with no knowledge in graph theory to model, collect, query, and analyze data in a network structure. SylvaDB provides tools for easy creation of schemas and modelling, automatic forms creation to input the data, collaborative features, a visual query editor, global and local search, reports charts generation, networks metrics, and visualizations tools.

From the website: NodeXL is a free, open-source template for Microsoft® Excel® 2007 and 2010 that makes it easy to explore network graphs. With NodeXL, you can enter a network edge list in a worksheet, click a button and see your graph, all in the familiar environment of the Excel window. (http://nodexl.codeplex.com/)

The book Analyzing Social Media Networks with NodeXL: Insights from a Connected World is the most comprehensive source on NodeXL. Accompanying slides and datasets are available on the NodeXL Teaching Resources page. (http://nodexl.codeplex.com/documentation)