Let's Hangout on Google Hangouts!
A free, 10-way video conferencing service that includes tools (like an electronic whiteboard) - and technically quite impressive. One-to-many video (like a teacher talking to a class of students) is hard enough to implement reliably with good performance... 10-way (many-to-many) video is an order-of-magnitude more difficult. Thanks to Google Fiber connecting thousands of servers, Google Hangouts works and works well. It is the best-of-class service available anywhere in the world. For free!