How to handle Events in PowerShell (another example of things you just can't do in a string based shell?) a GREAT example of how using PowerShell leads to .Net programming (and how knowing .NET programming translates into knowing PowerShell).
This article about accessing Alternate Data Streams in PowerShell is very interesting because it shows how easy it is to EXTEND a TYPE in PowerShell with some simple XML and a few lines of code. VERY cool.
Connect to WebDAV, FTP, Amazon S3, FTPS, or SFTP servers through a virtual drive which is a full file-system drive which works in DOS, PowerShell, etc.