According to Answers.com, the upcoming Sin City movie was shot entirely on green screen.
The Sin City movie is used of high-definition digital cameras, having the actors playing in front of a green screen so the background can be added later during the post-production stage. While the use of a green screen isn’t noteworthy, the use of High-Definition digital cameras is. The combination of these two techniques makes Sin City one of the few fully-digital live action motion pictures.
Movie comes out, April 1st.