Today is the anniversary of the death in 1996 of Carl Sagan, one of the most well-known popularizers of Astronomy. His Cosmos series "has been seen by 500 million people in 60 countries". He has an official site here. There is a memorial blogathon here,where posts in his memory are being offered. Perhaps billions and billions of people will participate. There are tribute pages scattered all over the web, including one at The Planetary Society. There are nice obituaries at CNN, APOD and CSICOP. Here is Carl Sagan's Baloney Detection Kit.
The memorial blogathon is being updated here.