Jim Truher just posted a script that he's been polishing for the last few months -- Background "jobs" and PowerShell. It's awesome, and one of the first things that people ask for once they start settling in to PowerShell.
What I love about being surrounded by a bunch of other PowerShell geeks is watching scripts like this come together. If I remember correctly, this script started off as a response to a question on our internal PowerShell distribution list. Marcel showed some examples of how to work with Runspaces through the scripting language, Jim added a bunch to it, and it quickly snowballed from there.
Even cooler, though, is watching the same thing happen outside of Redmond.