The premise of MeetingMade is simple: Just specify some attendees and some dates and times that work best for your meeting. Then each attendee gets an e-mail asking them to also mark their preferred date and times.
When you log in, you'll see a calendar heat map indicating the times with the highest consensus, and MeetingMade will point out the best options for your meeting.
Thankfully, only the meeting organizer needs a MeetingMade account, so you don't have to annoy clients and co-workers by asking them to join yet another online service.
What's more, MeetingMade is a better bet than Which Date Works, because it lets you specify specific times for the meeting, not just the best day. And while MeetingMade is free today (and throughout its beta period), it looks like you'll eventually have to pony up cash to keep using it.