Simple plamsa fx?

Right this is one way, simply draw your plasma effect to a texture.
So for exmaple:-
GLubyte MyTexture[Size_x][Size_y][RGB];

And draw you plasma to this, obviously Size_x and Size_y must be valid texture sizes.
Then if you want to update it every fram do:-

glBindTexture(GL_TEXTURE_2D, texture[PLASMA_TEXTURE]);
glTexSubImage2D(GL_TEXTURE_2D, 0, 0, 0, Size_x, Size_y,
GL_RGB, GL_UNSIGNED_BYTE, MyTexture);

I hope thats usefull, if you want any more info just ask and I''ll try and help, if I can.