ShadowClock

ShadowClock is a simple transparent analog clock for your desktop. Once installed the clock is located in the center of your screen and you can turn it off or adjust its settings by using the system tray menu.

You will be able to change the clock's brightness (meaning its opacity), size, and size of the hands (called arrows in this clock). Moreover, you can also add or remove a dial by clicking a small box. You can also change the position of the clock by clicking on the arrows and dragging them to the desired position on your desktop.
The trial version will display the word UNREGISTERED in the middle of the clock and will prevent you from saving the settings so that you won't have to adjust them every time you open the clock. Unfortunately, there's only one layout available, it lacks alarms, and you cannot hide the seconds hand or change the clock's color.
In short, ShadowClock is just a simple clock for your desktop which really doesn't offer anything that you cannot find in many other free clocks.