The Valve Company Publications Page now offers output from Valve's attendance at Siggraph 2010. There are slides from a presentation called "Water Flow in Portal 2" from a seminar on "Advances in Real-Time Rendering in 3D Graphics." From earlier in the year they also offer Game Developer's Conference presentations on "Rendering Wounds in Left 4 Dead 2" and "Shading a Bigger, Better Sequel: Techniques in Left 4 Dead 2." Thanks elvis.