A 16 minutes video on YouTube's infrastructure.

http://blip.tv/file/1069718/ - ~16 minutes. (Poor sound quality)
Mostly rely on open source software (MySQL, Apache, etc) and developing their applications with python.
Nice bit about tracing an error that brought down their systems down to a simple riser card which apparently was the root cause.
Nothing shocking other than that.
I guess it is worth the 16 minutes of your lifetime..