Over the past few years, I've done a lot of presentations on x64 technology as it pertains to game developers and DirectX technologies. Here is a collection of links for developers interested in learning more about the Windows x64 OS and x64 native programming generally.
64-bit programming for Game Developers (DirectX SDK)
RAM, VRAM, and More RAM: 64-Bit Gaming Is Here (Gamasutra)
64-bit Gaming Is Here Today - Where Are You (Gamefest 2008)
Why Your Windows Game Won't Run In 2,147,352,576 Bytes (Gamefest 2007)
Game Development for 64-bit and Understanding 64-bit Development (Meltdown 2005)