Fixing a date for anything - parties, meetings, socials, conferences, etc can be very frustrating. A brilliant site the Reverend Mrs pointed me to is Doodle. If everyone is on email, the organiser of a meeting can offer a number of dates and times via Doodle and then make invite everyone on the group. Each group member then follows the link in the email to their 'unique poll', clicks the slots they can manage, and Doodle records the results in a very handy table. It even keeps the total of the number of positive responses to each slot at the bootom, so you instantly know which is the most popular choice.
It's all free, and you don't even have to register (if you do, you get the use of additional facilities)