PowerShell 1.0 released for all but Vista
When I was working the TechEd Hands-On-Labs this summer, PowerShell (a. k. a. codename "Monad") was a very popular lab. Many administrators wanted to work with the product and have an early hands-on with it.
Well, version 1.0 for XP/2003 (x86/x64/IA64) has been released! You can go get it through the "how to download" page.
There is a lot of stuff online about how to use PowerShell; one nice article (although it's about 14 months old!) is at ArsTechnica, entitled "A guided tour of the Microsoft Command Shell".