I have started to use blogs in my class as a teaching tool. Since I teach physics, I'm not using it as a writing assignment, but rather a better way to communicate with my students. I'm also trying to eliminate as much as paper as possible.
I post their assignments to the blog and the students go there to get the assignment. I do this for homework and any classwork that they are doing as a group (I have 8 computers in my classroom). For assignments that include graphics or graphs, the students can email me their work. But, if the assignment is just text, they can post it as a comment to the assignment announcement. I have the comments moderated, so I don't publish them until all groups have submitted them. That way, the first group done is not giving away the answers to the other groups.
I also put an alternative assignment for any students that were absent from class that day. This way, they can check it from home and do the work on their own.
So far it is working out pretty well. Visit the blogs to check out what I'm doing. I'd appreciate any feedback and advice also.