NodeXL

Do you need to display and analyze a network graph but you don’t want to deal with difficult applications, arcane file formats, or advanced programming languages? NodeXL may be what you’re looking for.
NodeXL is a template for Excel 2007 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 a set of graph metrics. Networks can be imported from and exported to a variety of data formats, and built-in connections for getting networks from Twitter, Flickr, YouTube, and your local email are provided.

http://nodexl.codeplex.com/