If you havn't already investigated these web tools I recommend you take a look at Wiziq's virtual classroom and authorstream's power point presentation platform. Both are web based, have a bunch of features and free basic service.
I posted a response to your Engrade post. I need to know what is going on with Engrade. We love Engrade, but the student side has been down for over 2 weeks. This would not really be a huge issue, but half of our students take classes online and they are actually students in other districts. Unless we send them constant updates they have no idea how they are doing.