Via Byzantium's Shores, I found this suggestion to make Dec 20 (the tenth anniversary of his passing) a blogathon for Carl Sagan, endorsed by Nick Sagan. The "meme" is as follows:
If you're a Sagan fan with a blog, you can participate by posting something related to him on or near that date. Read or reread a Sagan book and review it; discuss cool things that you've done that's been influenced by him; pontificate on one of the many topics he treated (SETI, astronomy, critical thinking, the history of science, human intelligence....), or post about something completely surprising.
As I've mentioned before, I haven't read a lot of "classic" SF, and I've actually never read any of (either) Sagan's books (though one or two are in my behemoth TBR pile). However, the movie Contact had a profound impact on my life and will be forever listed among my Top 5 movies. I'll be writing about that movie and how it affected me on Dec 20.