I would think WSOP.com. They have live streaming coverage every year. From the looks of it, online streaming coverage won't start until Monday. Once it does you should be able to find the events being streamed at this link:
http://www.wsop.com/2016/live-video/
A copy of their full streaming schedule can be found here:
http://www.wsop.com/2016/2016 wsop live streaming schedule.pdf
I knew about the full schedule, but it didn't include the main event in July. Is it only on ESPN?