This looks like it’s both fun AND a great way to join in a Global Discussion on an Important Issue! I’m reprinting alot from the page of the website, as I want to make sure you get as much information as possible (and not all of use spend as much time on a site clicking around as I do). Sign up and make a difference.
What is Blog Action Day?
Blog Action Day is an annual nonprofit event that aims to unite the world’s bloggers, podcasters and videocasters, to post about the same issue on the same day. Our aim is to raise awareness and trigger a global discussion. The official website is www.blogactionday.org
How does Blog Action Day work?
From August 15th to October 15th bloggers are asked to register to participate so we can track how many are involved, as well as their approximate audience size. On October 15th the bloggers post on the issue and/or donate their day’s ad revenue to a charity involved in that area. We ask bloggers to try to keep their posting related to their regular blog topic so that posts are individual, suited to the audience and look at the issue in many different lights.

