For the online assessment and feedback it is important to be able to insert equations into the feedback but equations are a nightmare in web browsers. They can be displayed as images but this is not disability friendly. They can be entered as MathML but this requires special software to interpret the equations in Internet Explorer and different browsers look different. Then they can be displayed using a Java applet. This is what Blackboard does but it often crashes because of Java security issues!
The other choice is to use LaTex but I am not sure that is supported by all browsers but it does produce the best formatted equations.
The other major frustration is the need for images in questions and feedback and so I am going to have to use mash-ups and create a Flickr account and images to show the data and the graphs. This is all a major amount of work and shows that online learning can be very costly in terms of development time.