Beryl

Links
http://gentoo-wiki.com/HOWTO_nVidia_GL_Desktop_Effects

Configure
To ensure the compositing extension was loaded, run:

Next, select nVidia's OpenGL implementation and restart the X:

Links
http://gentoo-wiki.com/Beryl

Transpar�ncia padr�o
É na aba Window Management.

Habilite o Set Window Attribs by various criteria.

Ai em rules você abre o Windows Opacity e adiciona em window opacity

p:xterm:90