One can now hold such gatherings without actually having people all meet in one place via the use of the internet, using what is called a webinar, which is essentially a video conference involving several people that is held like an actual seminar.
Some webinars are able to attract people, while others can struggle to get any attention at all.
The above Youtube video is an example of such a service called webinarjam which helps you with all the technical set up and their new service webinarjam studio will even help with social media sharing to improve visibility of your live events.