My high school German students have begun to correspond with a group of Belgian students who are also learning German. My counterpart and I simply guide the students, prompting them to expand on their posts, to ask good questions, to think about the topics, etc.
The students seem to like it and they get a lot of practice using the language. As a teacher, I very much like the Moodle learning environment for this project. It's just a simple project, but Moodle makes it better.
If you teach a language, you might want to try a little project like this one.