Looking at the available “Synchronous Delivery Market for Learning” companies noted in this quest, there are only three that say they are free: Cisco WebEx, Google+ Hangouts, and BigBlueButton. They all look to be good for learning with similar features such as online meetings, recording, and playback.
Google+ seemed to be the best with mobile apps. For students, it looks to me that Google+ Hangouts would be the easiest to use and allows the most flexibility in what kind of technology to use, that is, laptop, phone, and notepad, etc. If students already has a Google+ account, they can login and get started right away. If not, they can easily create an account.
With Cisco WebEx, students need to contact a salesperson. With BigBlueButton, students need to download software and install on a server. Both of them seem more complicated and time-consuming than Google+ Hangouts.