http://www.doodle.ch/main.html
This is an awesome site for anyone who schedules meetings for people with multiple calendaring options. In my office, my boss has one calendaring system, then her boss has another. I can't tell who has meetings when and it's just recently gotten more difficult because IT is phasing out our calendaring system. Whew.
I think that this would also work for planning family reunions or just a simple party that you want the maximum number of people to be able to attend.
It's easy to sign up and use and the directions are simple.
Good luck fellow schedulers!
I could totally use this for our family! Thanks!