As we gear up for Fall Term and begin thinking about student projects, here are some more ideas about how students can collaborate online. You may even use some to hold office hours with students.
Using Google Hangout for Office Hours (via Inside HigherEd)
Video Conferences (in HD) using Zoom.us (by Macnn)
Here are two previous posts that relate to this topic as well:
What do you use? Contribute your thoughts in the Comments section.