I first learned about the Wilhelm Scream right after college, when I was getting more deeply into the nerdy, obsessive aspects of movies. While watching The Two Towers DVD, I noticed what seemed to be a very obvious use of the effect. That makes perfect sense, since those movies (particularly the Special Edition DVDs) are tailored for the obsessive nerd market.

So it's nice to see that someone has posted a thorough history of the Wilhelm Scream.