Recently, I had to set up a meeting for five people who have very different life schedules and also ideas about how to spend time. Here in Austin, TX people live pretty far apart and so if a meeting includes some people who live far north and others who live far south it is best to find a time when everyone is already in a central location. Most of the time I have no idea where everyone lives, so I found a great solution. It is called DOODLE.COM.
When they get the email with the URL it takes them to the site where they can indicate which times work for them. As each one fills in their best times you get email notifying you who has responded. In a short time you can easily see what time is best for the majority of the people and send them a note with the final meeting information! It is SO easy!
EVITE.COM. Evite is a bit more formal and has more information included. On Evite you can create an invitation to an event and people can sign up on a calendar. The best use I have seen of Evite is coordination of meals for someone who has just had a baby or is ill. Without tons of phone calls you can create a calendar that shows what is needed and when it is needed. People can sign up and even indicate exactly what they are bringing or offering to do and so you don't have lots of overlap in people's help.
I think that these two programs are examples of some of the best uses of technology to make our lives easier. Often technology just complicates our lives. It can be frustrating. The learning curve can be steep OR things don't work when you need them to. These two online sites have been reliable and VERY easy to use and saved hundreds of hours.