BigBlueButton is an active open source project that focuses on usability, modularity, and clean design – both for the user and the developer. It uses 14 open source components, such as Tomcat, MySQL, Open Office and Ubuntu. It supports sharing of slides (PDF and PPT), video, whiteboard, chat, voice (using Asterisk or FreeSWITCH), and desktops, which is very useful for online learners.