The Corporation (Mark Achbar, Jennifer Abbott, and Joel Bakan) weaves together dozens of interview clips to clarify the nature of the modern business corporation, its effects on society at large, and strategies for change. Despite feeling that it didn't adequately address natural resource issues or the positive side of business, I found this compelling documentary well worth watching when it first came out.
The recently-released DVD Special Edition is even better. A second disc with several hours of interviews (organized by person and by topic) adds depth and nuance. Web links for further information along with interviews with the filmmakers complete a remarkable video resource on why corporations act the way they do - and what can be done about it.