PowerShell & OpenXML
Eric White just posted an amazing set of Cmdlets on CodePlex. They allow you to use PowerShell to manipulate OpenXML documents to do all sorts of fun things, like create graphs from the output of PowerShell, automatically generate documents from XML, and extract comments from a document. Below is an 8-minute video introducing you to the technology and a blog post with more details.
James Brundage [MSFT]