Google Calendar

Of course, figuring out who has what time available is a critical piece of the puzzle. So something like Google Calendar could be very helpful in schedule meetings and conference calls and such. The advantage to Google Calendar over traditional calendaring systems is that it is cross-platform and cross-organisation. The users aren't tied into a Notes or Exchange server.

Google Calendar

However, there's still an open problem here. Given a moderately large number of users (i.e. more than three) finding a common free time across calendars is not a trivial task. Therefore, it would be really useful to have a tool that could examine several peoples calendars to find a common free time. One difficulty in solving such a problem is that in larger groups, not everyone will have the same calendar application. Such a tool needs to work across applications. Some sort of common micro-format or API would be critical to such a tool.