If you have friends outside of your own city, (or more specifically "longitude"), I've found a great application for thinking about them throughout the day:
EarthDesk is available for mac or pc, and replaces your desktop wallpaper, with a satellite image from space in real time. You can watch the sun and moon rise and set over the entire planet. Seeing where it is dark, where lights are on, what the cloud cover looks like, and where the sun is shining.
It's been awesome to open my computer and see how far along my brother's day is in Philadelphia, whether or not the Kingsley's are sleeping in Ireland, and I get to think about whether the Rhodes are going to sleep, or waking up.
It helps me to be more globally aware, knowing that my life represents just one perspective among many.
The trial version is free, and places a watermark in the center of you map, and it costs $24 to buy the offical version.
(The sun is about to go down in Philly)