Daylight Map is a segmentation of the Earth using the day/night criteria. You can add places on the map and even change the date. The site also shows you the local time for each place you add on the Google map. If you bookmark a permalink to the current state, you can check it later. I think this presentation is more attractive than some random world clocks.
You probably know that if you search for [time in city-name], the major search engines show direct answers at the top of the page.