I just downloaded the new TimeZone app. It Rocks! You will get a taskbar icon which displays up to 5 time zones when you hoover over it. The list is customizable. This app is perfect for people like me, who work with customers across 4 different time zones and are as lazy as me when it comes to calculating the time difference.
The only limitation is that you can add only 5 cities/timezones :-(
You can find the link to the app at our MSDN Canada page.