WhenIsGood is a free scheduling tool. The tool, which does not require sign-up or a password, helps to simplify the arranging of meetings and events.

WhenIsGood allows a meeting organizer to propose a slate of potential meeting times to invitees via email. In return, the invitees reply with information regarding their availability. Next, the results are tallied and stored for the meeting organizer’s perusal.

http://whenisgood.net/