Scott Leslie – who runs EdTechPost, is very impressed with Network EducationWare, an open source conferencing system developed by George Mason University. It includes the ability to share slides etc for a presentation, a text based chat, and a whiteboard. There is audio – both to record in advance with the slides, or for an audio chat session.
The slides themselves are distributed as pdf files, though can be uploaded in a number of formats.
There is also a video option, though due to bandwidth, George Mason haven’t used it that much.