I was just a kid when a copy of a little book (you know, books, the slow, analogue version of the Internet) titled Cosmos fell into my hands. That was my first encounter with Sagan.
What can I say about this genius that can't be found on Wikipedia and the rest of the Interwebzz?
For me he was one of the people who kick started my journey into asking questions, lots of them, opening my mind to endless possibilities.
Another blogger who once had the opportunity of introducing Sagan during a public lecture botched it up due to the emotions induced by the awesome presence of such a giant and introduced him as a 'curious fellow', much to the amusement of the audience and Sagan himself. Naturally he meant that curiosity is quintessential to a scientist but I think the other meaning is suitable too in a way.
Reading his books and watching him speak and gazing at the stars gave the feeling that the man knew something that few humans are aware of. This somehow permeates to the reader or viewer, for me being that there's so much more to life than the senseless bickering (understatement) that is plaguing this world, and that the universe is filled with such unimaginable wonders (or as Shakespeare would put it, there are more things in Heaven and Earth than are dreamt of in our philosophy, or something like that).
All we have to do is reach out with open minds, be true to ourselves and ask questions.
So go out there and find out more about Carl Sagan. If you're a book person then read his books, Cosmos on the sciency side, Pale Blue Dot and The Demon-Haunted World for the liberal arts major, and Contact for the SF nerd.
If you're not a book person then try and get the video documentary Cosmos: A Personal Voyage. And last but not least the movie Contact which, in my opinion, has one of the best movie intros, it really manages to capture the feeling that I mentioned earlier, to quote 'how small and precious we are', just YouTube it to see what I mean.
Oh, and he was also badass cool, getting arrested twice for climbing a chain-link fence while protesting the nuclear arms race.
And another movie you might want to watch, though not directly related to Sagan is Agora, which was released recently. I mention it because he had a certain fondness of Hypatia, who he mentioned in Cosmos on different occasions.
He was deeply involved with the SETI project, and it's a pity that he never got to make contact with an alien civilization. That's why I sometimes imagine that he's not really gone but was whisked away by some wise aliens and now is preparing the road for our contact with the rest of the universe.
ps. I've just finished watching the first episode of V (review coming soon) and the whole reptile thing reminded me of a funny Sagan connection. There's this guy who says that Sagan was a member of the reptile overlords/hamster eating frenzy because his name backwards spells Nagas, which is a snake-like anthropomorphic deity in Hindu and Buddhism. We truly live in a demon-haunted world, and if were not for people like Carl, the darkness would overtake us.