This video tutorial covers how to find you current location on an iPhone (all versions). This uses the map application, and triangulates your position between cell towers.
This video tutorial covers how to set world clock times using the standard clock application on an iPhone. This covers searching for cities in different time zones, and displaying them on your iPhone,
so you can easily view the current time all around the world.
This video tutorial covers how to use add a location to the weather application. This enables multiple locations for current temperatures and forecasts all around the world.