Many people want to have a calendar on their site for events. But there are other options or should I say places to have the calendar where others will find out about your event. Some may be thinking of oh, “the facebook events.” But unfortunately you only see events of people on your friends list. Good place to add events to for the purpose of having people you know return to your next event but not for new people to find out about it.
While google does have a nice calendar with an API to embed it onto your site it does not help in the promotion of the event either.
Meetup.com however does provide a method for people to see what events are happening close to them, and provides methods to search for groups that may not have a current event but they would have an interest in that type of event. Meetup does have an API to get the data from your group onto your site.
Not only does meetup help in increasing the numbers, have an RSVP system, but they also help in promoting your site as a link to your org can be included on your group page. It also helps in the public relations of your org because those who comment are members of the group and your meetup group will likely appear in the top ten results in search engines for people who want to know more about you.