You can create a course blog at: http://www.blogger.com/start
-- after creating your blog, go to "settings," and then "members" to add your students to it so that they can post. An email message is automatically sent to them.
Here is a handout you can give to your students explaining how to become active, posting members of the blog.
For more information about Wikis, see the article in this issue of the Romantic Circles Pedagogy Commons by Mark Phillipson on "The Romantic Audience Project."