Thanks to the magic that is XNA Game Studio Express 3.0 CTP, we can now put a clock on the Zune. Personally, I've always just relied on my watch, but I understand a lot of folks have wanted this.
Note that you need to have XNA Game Studio Express installed in order to build and deploy this software to your Zune.
Works On My Machine Disclaimer: This link carries exactly zero warranty or support. If it deletes files or kills your family pet, you have been warned. It might work great, and it might not.