This website is a nice introduction to powershell for people who are not familiar with it or are new to it intirely. I particually found the command shell walkthroughs helpful to me because of the images included makes this intro extremely easy to follow. It's helpful to both new and weathered powershell users.
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!