A backchannel is the use of networked computers to maintain several side-conversations while the main conversation is occurring concurrently. In higher education, a model of this would be an instructor lecturing about a topic with students collaborating in small groups at the same time. The Twitter Experiment at UT Dallas is an example of conducting a backchannel through the use of mobile technology.
This post at the Teaching with Classroom Response Systems blog outlines nine possible uses of backchannels in education as well as several examples of backchannel use at other universities. Check out the page at: http://derekbruff.com/teachingwithcrs/?p=472