Right now, if your study group corresponds to either HTML/CSS, Javascript, Python, or Ruby on Rails, you can propose a new hangout in one of the above Google Groups and invite people to join the hangout for the topic/tutorial you're interested in reviewing with others.

In the near future, though, my hope is that a platform will replace the Google Groups and make the study group creation process around supplementary resources (besides the ones I picked to experiment on, that is) much easier. Can give you updates on when the beta platform is up if you join the mailing list or send me a PM.