My students use the Mixxer from Dickinson College in Carlisle Pa, very successfully. I teach hybrid and online courses and I require a language exchange with a native speaker for regular practice. The best part of the Mixxer is that both students are learning each other's language, so they alternate in role of teacher and learner. The exchange is well-moderated by the Mixxer administrator. There is also an active Facebook associated with the project.
Best,
Laura Franklin Northern Virginia Community College