I think I first heard about "The Last Lecture" via a book request we got at the library.  The Amazon page for the book has more info including a couple video clips explaining the background and significance of this particular Last Lecture.

A bit more searching revealed that the full video of the original Last Lecture presentation at Carnegie-Mellon University is on YouTube (of course). 

It's an hour long clip but if you watch the first couple minutes, there's a good chance you'll want to watch the whole thing.