"Cooperative Linux is the first method for optimally running Linux on Windows and other operating systems natively. It is a port of the Linux kernel and support code that allows it to run cooperatively without emulation along with another operating system"

Native Client is an open-source research technology for running x86 native code in web applications, with the goal of maintaining the browser neutrality, OS portability, and safety that people expect from web apps.

"designed for individuals and corporate users who need to use both Linux and Windows applications within the same desktop environement." - another coLinux thingie

"installs Linux on top of your Windows operating system, allowing the two to exist side by side and even interact with one another."