The Observer has posted a list of the[ir] 50 Greatest Arts Videos on YouTube, among them Zora Neale Hurston singing "Uncle Bud" in 1939 (click to view; embedding option disabled for these videos), Madonna's first stage performance as a recording artist, and Marlon Brando's screen test for Rebel Without A Cause. Many of the post's commenters add links to their own favorite arts videos.
I know I sound like a naif, but YouTube still blows me away. I never could have imagined I'd get to see a scene from the 20th century theatre event I most wish I'd witnessed: the 20-yr-old Orson Welles's all-black "Voodoo Macbeth" from 1936 (not on The Observer's list, but on mine). Scene begins after newsreel-ish bit:
Of less historical interest, but sweet and sad: an affable, genuine Welles at 70 being interviewed by Merv Griffin. He died two hours after the interview was taped.
One more. Welles was a magician and fascinated by all kinds of fakery and sleight-of-hand. In this short clip, he describes his one-day stint as a successful fortune teller: