One of my favorite Metacity themes is "Unity" by bvc:
Unity always uses GTK's selected background color for the window with focus. This doesn't always work for everyone; especially if you want a plain, glassy decoration.
Unity Albino is a hack of Unity, so that it always uses the base GTK background color. The title text has also been changed to black.
The download contains folders to manually drop into your themes folder, and an Ubuntu .deb package.