I have been able to locate, on-line, three commencement speeches given by Ray Bradbury to college graduates. (I should have been so lucky to have such a speaker...I can't even remember who gave my commencement speech.) I am going to post these three entertaining talks in chronological order in this thread. The first was at CalTech on June 9,2000:

https://www.youtube.com/watch?v=NLCdhkUlKqQ

The second was at Clarement McKenna in 2001:

https://www.youtube.com/watch?v=MKP7_atK3u4

And the third was the speech given by Ray at the commencement at Chicago's Columbia College in 2009, where he was introduced by Sam Weller, a member of the faculty at that school:

https://www.youtube.com/watch?v=sqm5uRCJ9vg