Disclaimer: I deserve no credit for the countdown itself, I took the basic program from http://customize.org/rainmeter/skins/64647 and edited it. I'm not too familiar with the Rainmeter setup, so I needed somewhere to start.
I noticed a few threads on countdown timers, so I whipped something up and thought I'd share the result. My current setup is an always visible display using Rainmeter. I can move it around so it shows up anywhere I want on my desktop, or I can move it down to my taskbar, and move it to the topmost layer, and, BOOM, I've got myself a countdown meter that sits on my taskbar!
Here's a http://img194.imageshack.us/img194/2544/desktopcountdown.jpg.
The guy is optional, and can be turned off to only display the text countdown, as he is a little bulky, and mostly there for fun. You can also mess around with the font, size, color, wording, etc.
If anyone wants me to make my setup available I suppose I could, just let me know and I'll get it packaged up and uploaded.