From telepresence to skype...
All you need is a large screen, a microphone, a teenager (to operate the technology) and a Skype account.
Virtual meetings can be very effective and useful if used in the same country but at the same time they can be a nightmare when dealing with overseas customers. Often sites can crash and there can be connection issues. In my experience it is always best to meet face to face. It can allow you to build a much better relationship with a client or customer. Meetings abroad can be an issue but there are sites like www.incentivetravel.co that can arrange venues etc for you. In my eye, face to face meetings are much more beneficial than virtual ones.
Virtual meetings whether one-to-one or one-to-many are unavoidable these days. It is not always possible to fly across the world for a few hours if you have outsourced aspects of your business or use services and partners based in other timezones.
As a company we've used skype (on a daily basis) , joinme & gotomeeting to liase with tech teams, sales teams and partners around the world. And while these may not be the same as face to face meetings, virtual meetings are often more cost-effective and time-saving, and work extremely well in our organisation.