Doodle

Doodle is an excellent web app that allows a bunch of people with disparate and complicated schedules to determine the optimal meeting time or date among them. It is the easiest of these types of tools I have tried, and does not require people to register or do anything other than fill in their name and check off boxes. It is free. Doodle has advanced features that allow you to do “if this, then that” type of scheduling as well, but I have so far just used the basic set up.

-- Alexander Rose  

Doodle
Free
Available from http://doodle.com

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