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.
Skype is VOIP and instant messaging software that allows voice and chat communication between computers and phone systems via the internet. Direct computer to computer via the internet is free of charge, and computer to phone connections via the internet have a relatively small fee. Additional features include video conferencing and file transfer. Acquired by Microsoft in May 2011.