October 15, a week from Monday, is Blog Action Day, and the theme this year is the environment. If you have a blog, use that day to post something related to the environment, in whatever way, shape, or form you prefer. So far, over 7,000 blogs have signed up to participate, with more joining every day. (Not that you have to sign up or anything, but it helps them measure the impact.)
If you're thinking 7,000 blog posts isn't that much in the big scheme of things, Blog Action Day estimates those posts will reach nearly 5 million readers. Putting environmental issues in front of that many people can have a huge effect on public consciousness, and awareness is always the first step in change. So who knows what big things may be set in motion by the combined efforts of individuals sharing their ideas. See the Blog Action Day blog for more on how bloggers can change the world.