An example of what's possible with ps1xml type deffinitions, and how you can improve on the default Add-Type, and use ps1xml the way you use extension methods in C#
Connect-WebService allows you to connect to a remote webservice via it's WSDL service description file, and generates the web service proxy for you -- like wsdl.exe would, but straight into memory in PowerShell!
Hidden Start (or Hstart) is a small app that allows console applications (including PowerShell) to be started in the background without any visible windows.
Not because you really needed another ASP.Net language, but because sometimes, a web page would just be so much easier if you could just take advantage of that powershell cmdlet...
An Open Source, cross-platform media-tagging library with support for ID3, ASF, APE, Xiph, and other media tags embedded in everything from .asf to .wv including mp3 and mpeg4, wmv, etc.\n\nSupports a large variety of movie and music formats and abstracts away the differences so you can just write: file.Tag.Title, file.Tag.Duration ... etc.
SourceCode and Compiled Binaries for two low-level system information tools: NtSysInfo explores Windows internals and enumerates system processes, windows, threads, objects. The WhoUses utility allows you to determine what process has a file or DLL locked.
CertMgr is a new tool for the management of certificates, certificate trust lists (CTLs), and certificate revocation lists (CRLs). It is installed in the \Bin folder of the Microsoft Windows Software Development Kit (SDK)