If you have a wordpress site try one of these: http://premium.wpmudev.org/projects/category/plugins/?s=calendar
In addition to the great advice that Trishul has shared, I’d like to add that your event is also a business. As someone who produces my own live events (sponsorshipbootcamp.com) and speaks at the events of other promoters (author101university.com, movepeopletoaction.com, etc)... one of the bigges...