In the November 2008 installment of our Windows PowerShell column (which is available online), Don Jones demonstrates how to create a tool that will inventory the operating system build number (this is one of the best ways to determine the OS version) and service pack version number from a list of computers.
This is a very useful tool in itself. More importantly, however, Don uses this example to walk you through the process he uses to develop a script. After all, the process can be applied to countless projects you might encounter. Once you understand and can reuse this development process for your own tasks, you'll be well on your way to solving nearly any administrative problem using Windows PowerShell.
Don has also provided a video screencast in which he demonstrates this Windows PowerShell-based inventory tool and guides you through the process he used to build it.