Check out the assistant toolset for generating, controlling, managing, and configuring X11 in your system. Create a customizable environment with options to modify source code, selected windows, interleave the X11 elements with Aqua components, implement scripts, etc.
OroborOSX is an X11 environment designed for use in rootless mode with XDarwin on Mac OS X. The source code is also available.
Wineskin Winery creates Mac OS X ports/wrappers for Windows programs/games, with an easy-to-use GUI, integrated Wine, X11 and an installer.
LiquidMac uses a particle system to imitate liquid and responds to laptop orientation.
