My county uses Blackboard Collaborate (formerly Elluminate) for our online classes (and will soon be letting teachers use it for their own purposes). But you can use Big Blue Button for free to teach your students (as I tell my students it could mean the end of snow days) online. Not only that, but think about how you could have meetings with teachers from across your county, state or the US. For example my county has an annual meeting between AP teachers and this would be a good way to do it. As you can see from the video above you can record your screencast, see the other participants (if you choose), have a whiteboard, can share your desktop or just show a PowerPoint. There are also a bunch of tools, such as being able to mute students, an IM board for the entire group or for one on one and more. Oh and best of all it is entirely FREE!