Stephen recently wrote
What I would love is to be able to offer - selectively or publicly - visibility into my calendar, with ACL based write access that's easy enough for anyone to use. The sheer amount of time this would save come conference time, when 10's or 100's of people are asking for time with us, would be worth its weight in gold. It would allow us to push the burden of scheduling onto those who request our time. You want to meet with us? Great. Here's the schedule, knock yourself out.
I totally agree this is the BLOG tool for the collaborative scheduling. What needs to be built is a standard way to export the calendar entries , I think iCal has a good shot at it and then some tools can be built to intermediate the negotiation. Another use case is where you don't really want to show all your calendar busy times but only show a view/subset of it. Anybody interested in collaborating on this one?