BigBlueButton is a live, eClassroom module. It supports Whiteboard presentations (PowerPoint imports) screen sharing of local programs, voice, webcam, text chat and online quick poll audience responses etc. Presentations can be recorded for later playback.
Full participation requires a computer with Adobe Flash Player. Screen/Application sharing requires Java. Recorded playback can be done on any device. Participation can be done via iPad with the third-party App named "Puffin Browser". Free ad supported version or $3.99 full version with no ads (recommended). iPads/Tablets do not support Java at all, so no screen sharing can be initiated via iPad/Tablet.
This is a brief 8 min. "How-To" overview of Big Blue Button.