Meet with Approval

Their website explains it pretty well:

"Arrange a meeting or event. Work out which day is good for everyone & Keep track of who is coming.
'Meet With Approval' could not be simpler. Fill out the form which creates a meeting page. Your friends or colleagues are notified of the event. They visit the meeting page and help decide a good date. When you are all happy, 'Meet With Approval' confirms the arrangement and you all meet up. Best of all it's FREE!"

Go to the site and check it out!