This lecture is on achieving your childhood dreams, most of which he did, and on enabling the childhood dreams of others. Pausch was the founder of the Alice Project, which is a 3D programming environment for teaching students.
UPDATE (July 26, 2008): I'm getting lots of traffic to this post from people searching for Randy Pausch's name and the word "atheist," apparently from people trying to find out if he was an atheist. His CMU web page thanks his church, so he belonged to one, whatever his religious beliefs may have been. He didn't say anything in his lecture to indicate what they were. As an atheist, it doesn't matter to me so much what he believed, as opposed to how he lived. That is in sharp contrast to several Christian sites which have condemned him for being a nonbeliever (which they don't know to be the case) or for failing to evangelize. These people strike me as angry believers looking for reasons to criticize someone who led a good life. One Christian writer criticized Pausch's talk by attempting to paraphrase it as "I lived a meaningless life following meaningless rules, so should you." The same writer says, "Yes, he lived a nice and successful life, but so what? Who cares? He will be forgotten as were many people before and after him. His impact on the world would soon disappear. Whatever he achieved in research will soon become useless." What nonsense! So what? Those who knew him and worked with him disagree. He will eventually be forgotten, as we all will, but it will always be the case that he did live and he did make a mark on the people around him and his time was not wasted. And he will be no more harmed by his nonexistence after his death than he was by his nonexistence before he was born.
I question the motivation of those who argue critically of those who have lived happy and productive lives, arguing that so much better are the lives of those who live miserable, angry, critical, and destructive lives, just so long as they accept Jesus before they die. Surely the universe they want to believe in is an unjust and immoral one.