I started enjoying riding my bike around 2003 (just had this tank of a cruiser, yipes). In 2004, I was staying at my parents' for a few weeks after doing some summer contract work out of town, and the first morning I woke up in their basement, lying on the pullout bed in front of the TV, flipped around and found the Tour de France on OLN (the network that has it in Canada). It was just after Voeckler got yellow. I was fascinated. The tactics, the strange cooperation of riders on opposite teams in the break, the cumulative time game... it was fun to follow, to watch guys get seconds and minutes. And it was fun to cheer against 'a certain Lance Armstrong', because I've got a thing against predictable dominance. But man, the memory that sticks out most was stage 17(?), when Landis burned everyone but the top 4 off his wheel and went for the stage, with Kloden timing a perfect counterattack (didn't realize at the time how rare a Kloden attack was) and Armstrong closing a ridiculous gap to pip him at the line. That hooked me, and made me grudgingly say chapeau to the man I was cheering against.
So that was the TdF. Then in December 2006, I found this online history of the Tour, year by year (no longer available for free, I think, as it's been made into a book) that this guy wrote. I read it twice. They kept referring to other races guys had won coming into the Tour, and I realized there was a whole season. I mean I knew there was, but I realized how important and storied the other races were. I started following cyclingnews daily in 2007, and have dedicatedly watched races online since the start of 2008 (and have convinced my friends to do so as well).
As for racing, I've never done it, other than bike messenger races (that's my job) - I've been to the world championships of that twice. It's... uh, a little bit different than road racing.