CoSketch - CoSketch is a multi-user online whiteboard designed to give you the ability to quickly visualize and share your ideas as images. No registration or plugins required.
GoToWebinar - Webinar & Online Conference | GoToWebinar
IDroo - A shared whiteboard for use by multiple Skype-users simultaneously. Features
Zoom - Equip your team with tools designed to collaborate, connect, and engage with teammates and customers, no matter where you’re located, all in one platform.
Scribblar - Scribblar is a free online collaboration tool that is perfect for online tutoring.
WebEx - Cisco WebEx Web Conferencing, Online Meetings, Desktop Sharing, Video Conferencing