the new Anthropologie in London (first in Europe) has a living wall--irrigated solely by rainwater collected on the roof! I've always loved living walls--the local Seattle zoo has one in the tropical rain forest house with orchids that is pretty spectacular when they are blooming. (Anthropologie wall pic from Print & Pattern).
A few others to admire...
From mosstika, installed on a roof garden in Brooklyn. Little tiny green sedums growing from between wood slats of varying sizes. (more photos of the process at designboom). Followed by a few more installations by Edina Tokodi of mosstika. I love the living graffiti idea of many of her pieces.
America's largest green wall (the size of a doubles tennis court!) by PNC in Pittsburgh. When watered the required 15 minutes a week, it weighs 24 tons.
Patrick Blanc appears to be the master of the living wall, or vertical garden as he calls it. Check out the slide show on the opening page of his site. Crazy.