PowerShell with its .NET integration and more and more products/platforms shipping with native PowerShell cmdlets is a great tool for automated testing. (I even posted a sample PowerPack helping organize tests in PowerGUI a few years ago.)
We at Quest Software are using PowerShell a lot for our software development and testing. Our SharePoint management team is on the cutting edge and extended acceptance testing Fitnesse framework to PowerShell.
But wait, now it gets really cool: they have open-sourced the PowerShell Fitnesse framework – PowerSlim at codeplex for everyone to download, use, modify, and update!
Read more about PowerSlim in Konstantin’s blog here.