Last night the guys from Mindscape unleashed their powershell gadget onto the world. This very cool gadget allows you to enter powershell commands into a gadget rather than having a powershell window running full time in the background. The guys have actually hooked up their sound system to a system that plays MP3's and using powershell they "bump" and play tracks. So the gadget was inspired in many ways by this scenario. The gadget also has a nice flyout which serves as a powershell window that tucks away when not in use - very nice.
The other interesting thing about the powershell gadget is that it uses .Net but without requiring a UAC prompt or MSI installer to make it all work - thus, you get full .Net power in a sidebar gadget that any user can install and use - very cool.
You can download the gadget here, and read about how you can automatically register any objects you need here. If you get it - make sure you install powershell before you tell them it doesn't work... :-)
You've seen JB using .Net from inside a gadget and you've now seen the Powershell Gadget that uses .Net, Vitorrio has taken to the next level by using Windows Card Space in a sidebar gadget. He's also written a pretty comprehensive blog post that tells you how he did it and he's attached the source from his project to his blog post.
Very cool! Hopefully these help you expand the possibilities you can acheive with gadgets :-)