If you work or interact with people in different countries you'll know what a pain it can be to coordinate a meeting with the parties are in different timezones. Even something as simple as getting three people on the phone can be tricky when one is in the US, another is in Europe and you're in Australia. World Clock for Remote aims to simplify that task
There are dozens of clock apps in the App Store. World Clock for Remote takes the approach of letting you add people from your address book to a map of the world that gives a visual representation of what time of day it is for them.
Having worked with people in different timezones for some time I now remember how to calculate the time differences in my head. As a Mac user, I have iStat Menus installed and its enhanced clock keeps a list of several timezones a click away.
World Clock for Remote [App Store]
iStat Menus [Bjango Software]