Lots of resources on the net; blogs, script repositories, books, podcasts and such.
I have been reading a tutorial designed for people who don't know object oriented programming. As my scripting skills were developed a century ago. There hasn't been an opportunity to think OOP since the LISP days at IntelliGenetics. This introduction with explanation of OOP terminology/thought is very helpful. I imagine it would be a bit slow for someone versed in .NET or C++. Check it out on the Microsoft site, Sesame Script.
I am using the book Microsoft Windows PowerShell 2.0 Programming for the Absolute Beginner by Jerry Lee Ford to great effect. Reading it cover to cover and doing the example assignments. After completing chapter 3 I felt that I could re-write any script I've created in csh|sh|ksh into PowerShell. So no problem going forward building scripts at work (check off one 2010 job goal;).