I just bought the Animatrix on DVD and let me just say this... It was incredable. The animation is top notch and very stylish but the plots to the 9 short movies are even better in most cases. I believe you can see four of the movies for free at www.theanimatrix.com so check 'em out. They really offer a cool expansion into the cool settings and concepts that the Wachowski brothers created.
...I'm afraid that the 'Alien' series may have taken a back seat to my new obsession.