This free tool called Microsoft Time Zone runs as a tiny icon in your system tray and allows you to watch the current date and time of upto 5 cities around the world simultaneously.
Microsoft Time Zone also lets you compare times at different places in the world without changing your system time. Would be of great help when you are scheduling that next meeting with a client who's on the other side of the Pacific. Thanks Sudhakar.
Alternatively, you can keep an eye on the current time around the world with any of these Visual World Time Clocks or use search engines like Google, Yahoo or Ask.com to find the current time in any city around the world.