A more direct link to the CARL SPARC Author's Addendum is available at: http://www.carl-abrc.ca/projects/author/author-e.html.
Although the Addendum was just released this morning, it has already proven to be very useful! When Editors or Publishers contact me about potential articles, book chapters, etc., as an open access advocate, naturally one of the first things I need to clarify is whether my work can be made openly accessible if published in this particular publication venue. Pointing to the CARL SPARC Author's Addendum is a great way to explain the rights I want to retain!
What if the publisher will not accept the Addendum? No problem! I have far more opportunities to write than I have time for anyways. If some possibilities need to be eliminated, the ones with limited dissemination (or, as Jim Till might put it, aiming for obscurity) I can let slip!