Randy Pausch is a virtual reality pioneer, human-computer interaction researcher, co-founder of CMU's Entertainment Technology Center and creaor of the Alice software project.
Randy is dieing of Pancreatic Cancer and in September last year ('07) he said goodbye to his students as his "last lecture" at Carnegie Mellon University.
In this video, he gives a reprise of this last lecture on the Oprah show which has been downloaded over a million times.