Twiddla is a real-time online collaboration tool that is free and easy to use. You can mark up its whiteboard, annotate pictures, websites or documents that you have uploaded, and even work on an EtherPad (aka TitanPad). Twiddla also incorporates text and voice chat which allows real-time interaction with people from all over the world.
Once you sign up for a free account, you can manage your meetings’ settings (i.e. make them private or public, change their URL, limit who can use the whiteboard). You can even play back the entire meeting or view its full transcript.
Check it out here: http://www.twiddla.com