iPhone: Converting between timezones can be tricky sometimes. If you're looking for a simple way to glance at the time across the world, Klok is a Notification Center widget that does just that.
Once Klock is installed, you can create multiple clocks to look at the time in a variety of time zones. You can also tap on those clocks to convert the time instantly, which makes setting up meetings between different timezones a lot easier. It's a simple thing, but it works well and doesn't have a lot of clutter.
Klok (free) [iTunes App Store]