Student Response Systems aka classroom clickers

ClassInHand                                                           http://classinhand.wfu.edu
Classroom Performance System                            http://einstruction.com
Discourse                                                               http://www.ets.org/discourse/
Hyper Interactive Teaching Technology                  http://www.h-itt.com
InterWrite PRS (Personal Response System)         http://www.gtcocalcomp.com/interwriteprs.htm
Numina II student response systems                      http://aa.uncw.edu/numina.srs
Qwizdom Interactive Learning System                    http://qwizdom.com
TI-Navigator                                                            http://education.ti.com/navigator
TurningPoint                                                           http://turningtechnolgies.com