We have recently set up classroom wikis with PBWiki.  Our goal is to have students post their narrative writing pieces on the wiki and then have their classmates respond to and edit their writing.  We will limit the access to these wikis and have teachers view any changes that students want to post before they are posted on the wiki.  This idea came from different sources: looking at classroom wikis online and a suggestion from teachers at another school in our district.  It will be fun to see how this idea develops for us, especially in the coming school year.