Location, location, location
The location and time zone setting in the latest version of Gnome - the one that shipped with Ubuntu 8.10, is great:
For the uninitiated, Gnome is the graphical front end of Ubuntu Linux.
The selected location shows the current time and date at the place you’ve set as your current location, as well as the weather and temperature. Clicking the date and time reveals the view above, with a calendar, time zone map and list of the locations you’ve added.
Adding new locations is intuitive, I found it in 10 seconds without having to Google anything, and once you’ve added a location it stays in the view that opens when you click the date/time display. Easy, and displays lots of information without getting in the way. The weather icon is a particularily nice touch!

