Scheduling meetings is hard but it is a lot easier when all of the participants are on the same calendar server (Google Apps, Exchange, etc.). Despite all of the advances in calendaring, coordinating with participants in other companies hasn't gotten much easier in all the years I have been working. Yes, there have been little victories here and there like Doodle and Tungle (which looked promising until RIM bought it), but overall, we are still sending times when we are available and hoping we stay available. This is an increasing problem as business relationships become more dynamic and less siloed by corporate boundaries.
Google Apps has taken a step in the right direction by creating a free/busy view of your calendar that you can share. But I don't love that option because that gives permanent access to that view. It would be better to generate an expiring link that would give the user a view of the free/busy times for a few days (until the meeting is scheduled).
Google, Microsoft, anyone in the calendar software business - please steal this idea! Just don't patent it so that only one customer community benefits.