Having family all over the globe makes for an interesting life, but sometimes it's hard to know which end is up—or more importantly, who is up when. Enter FoxClocks, an add-on for FireFox, which has made that task much easier for me. There's also a version for Thunderbird, and I use both to my advantage.
My two favorite display formats are (1) showing the city, time, and day in the status bar:
and (2) a tiny icon in the status bar which pops up that information when I hover my mouse over it.
