Collaborating with 4th/5th graders

I am a tech teacher of 4th and 5th graders (& other things). I am trying to find ways to give many of our students an audience for their work. Many of them are struggling readers/writers. They might create better pieces of writing if other students from around the world are reading their work. I have students who are creating web pages through pbwiki.com. We would love to have a sort of "pen-pal" who can view our work and leave comments on who they are and what they have done, hopefully we could read your work as well. pbwiki could also afford both of our collective students a place to collaborate online and create projects together. Any takers out there?