A web service where everyone has a "profile", profiles can be grouped by company, by office, by all sorts of things. Every profile keeps information on the persons location and the relevant timezone. If someone needs to arrange a meeting they select the relevant profiles ("SF office, NY office, contractor #14") and it provides all the relevant timezones, maybe even with the options to "automatically" calculate the best time to arrange a meeting for all the parties involved. Tie-ins with google calendar and the like.

We use Skype and so I rely on Skype to tell me what time it is locally for the employees I'm interested in, it works but it's far from elegant.

Maybe I should build this.