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:
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.
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