Joel Schlosberg has an excellent idea: on December 20, the tenth anniversary of Carl Sagan's death, there will be a blogathon to commemorate what Sagan did for humanity. It's also been endorsed by Carl's son, Nick Sagan. There will also be a version of the blog carnival Skeptics Circle the day after the blogathon which will be dedicated to Carl too.
I was profoundly affected by Sagan's work, as have millions -- billions -- of others. I will think carefully about what I want to write for this. If you have a blog, astronomy or otherwise, consider writing something as well. Sagan brought joy and wonder into our lives, and he made it OK for scientists to popularize science. We owe him so much.