PHP Advanced tutorial:

http://www.killerphp.com/tutorials/advanced-php/
I found the first 8 lessons of this on Youtube and ended up purchasing the whole set because I really like the way it’s done. Jon’s description is clear and no watered-down stuff.

Scaling:

Even if it is only a slide show, I still learned lots of key points. You can always look up the extended definition of each points.

Scaling Facebook with OpenSource tools