NodeXL
NodeXL is a free, open-source template for Excel 2007 and 2010 that lets you enter a network edge list, click a button, and see the network graph, all in the Excel window. You can easily customize the graph’s appearance; zoom, scale and pan the graph; dynamically filter vertices and edges; alter the graph’s layout; find clusters of related vertices; and calculate graph metrics. Networks can be imported from and exported to a variety of file formats, and built-in connections for getting networks from Twitter, Flickr, YouTube, and your local email are provided.