As inspiration for your blog-a-thon post, here's a collection of cool stuff related to Carl Sagan that's available online.
A 1994 CSICOP keynote by Sagan on Point of Inquiry, together with a new interview with Ann Druyan. A transcript of the keynote's Q&A session was rediscovered and published in Skeptical Inquirer magazine in 2005.
Ann Druyan also discusses Carl in an interview by Skeptic magazine's Michael Shermer.
A NASA video of a 1972 panel on extraterrestrial life, also featuring Ashley Montagu.
Carl Sagan on Charlie Rose in 1995 and 1996.
Carl Sagan on MySpace.
The website and blog of Carl's son, science fiction writer Nick Sagan.
The website of Don Davis, space artist who illustrated such Sagan works as Cosmos and The Dragons of Eden; including his memories of Sagan.