It can be damn near impossible to get a large group of people to agree on a time for a meeting, party or any other gathering.
Doodle.ch has got the solution. If you are trying to organize an event, but can't figure out a good time, their site allows everyone to define their availability, and then everyone can see when the best time is.
The best part - no cost. the second best? no registration or logins required (although you can if register/logon to access more features).