Doodle

I've known about and used Doodle for a couple of years now.  Doodle is a website that helps groups of people schedule meetings.  If you are the person that is creating the Doodle, you select the days in which you think the group can meet.  You then send out a link to everyone in your group.  Your group members then select which dates they can attend the meeting.  Everyone will then be able to see which date works best for everyone involved.