Analog Clock is a handy tool that allows you to replace your boring Windows by a customized one. The program offers many skins of both digital and analog clocks, so you can choose the most suitable for you. Also, if you mouse over the clock you it displays a skinnable calendar that shows the current month and marks the day. The clock sits silently on your system tray and you can change the options from there. This is an an NTP-enabled application, so it will synchronize your clock with atomic clocks through the Internet using a server you specify or any, and will automatically update your system clock. All the skins are completely customizable, allowing you to enable/disable some of the interface elements, such as the second hand. It also provides quick access to Windows date&time properties to make this task even easier and fast. All in all, if you are just looking for an application to replace your boring Windows clock and you don't need any other tools, Analog Clock may work for you.
It supports Windows XP or later and is absolutely free.