ScriptCenter has a couple chapters of Bruce Payette's awesome book:  Windows PowerShell in Action.  You can (and should) read part 3 of chapter 10 at:

http://www.microsoft.com/technet/scriptcenter/topics/winpsh/payette3.mspx

Part 3 focuses on XML processing.  If you've ever been coding XML and thought to yourself, "this is like kicking a dead whale along the beach", then you'll want to read this chapter.

Enjoy

Jeffrey Snover [MSFT]
Windows PowerShell/MMC Architect
Visit the Windows PowerShell Team blog at:    http://blogs.msdn.com/PowerShell
Visit the Windows PowerShell ScriptCenter at:  http://www.microsoft.com/technet/scriptcenter/hubs/msh.mspx