Xfce
Starting with version 4.2, the window manager of Xfce, Xfwm, integrates its own compositing manager. Other compositing managers exist, but have been very unstable, and Xfce was the first to put its own compositing manager into the window manager. At its beginning, many users called it the most stable one available, though at the time, in late 2004, xcompmgr was the only other compositing manager available.