I just finished a test of the version 3.5 version of DimDim and I was amazed with how far they have come! In their next release (v4), they have promised Mac Compatibility with screencasting as well as the ability to record meetings!!!
Being able to record meetings is huge! Imagine being able to run through your training and record the video and powerpoint/screencast and then be able to reuse that piece over and over. Then after someone watches the training video, they can meet with you virtually via DimDim to ask questions etc. Positively amazing and free! (Big plus for tech savvy schools)
Not to go on and on about how surprised and pleased I was with the DimDim product, but they also offer a free version and a $99 a year version that would meet the needs of most schools. The best part about this route for schools is that those who do not have the infrastructure can use the free version and not have to isntall the software on their server.
Did I mention there is a plugin for Moodle Online Classrooms! Yes, it is fully integrated with our online learning environment where students could use this meeting and communication tool to work on projects from home or meet with classmates to discuss homework etc.