Organizing meetings, training sessions or events by email often takes ages or never happens. However, there is something I have been using along with many other people I know. Doodle.com. It is easy to use and you can give people various dates and times and they simply select when they are available.
It is free to use although there is a premium option which allows for calendar integration, sending automatic reminders, missing responses and some other useful features.
Here is a short video tutorial to show you how easy it is to use.