In comes our hero to the rescue Doodle! You can even use this tool without registering. Simply go to this site: http://www.doodle.com and you can schedule an event on the fly. Put all the dates into the calendar provided then create the event and they give you a link to send to all the event participants. They then go to the site and highlight any date they are free; the tool then shows which dates where everyone is free! So easy to use - give it a go!