Another option for blogs is 21classes (http://www.21classes.com/). Ed accounts are free and have a short learning curve. Unlike blogmeister, it has an up-to-date look and easily handles widgets that might be appealing to users: embedded media, poll everywhere surveys, etc. Each blog and/or post can be private, published to only the class group, or public; teacher managers can manage visibility of any post and also moderate blog comments.
I love how easy pbworks makes wikis for teachers (down to a print and cut username/password sheet to share with students), but pbworks is clunkier in terms of page layout and image manipulation. Wikispaces has just added an easy student accounts feature as well, and is more flexible regarding layout and image tools. In Burlington, we had students as young as 1st grade using these tools pretty successfully.
Give a shout if you'd like to see examples of our students' work.