I've been using a very simple system of a course blog with a blogroll of all the student blogs. I wrote instructions for my students that they don't seem to have taken very seriously. I think the main change I would make the next time is to schedule several dates during the semester when I will grade the blogs--too many student are putting it as low priority because it isn't graded until the end. For all my students this is a course outside their major and it is hard to get them engaged because they have much higher priorities.
I tend to be a believer in very simple systems, but I can see several features that would make my job easier. Some way of automatically adding students sites to a blogroll would help, and even more so a blogroll that automatically listed the sites in order of how recently they have been updated. I spend too much time going to student blogs that haven't been updated since I last checked. Automatic trackback would be wonderful, and I think would help make the blogs more of a community for my students.
I know there is software out there to do those things, but I haven't taken the time to find out how to do it. I would love a system that did all that for me.