I was a bit of a latecomer, 2004. As a 24 year old in Canada, cycling didn't get mainstream exposure too much, but I happened to finish some contract work out in the woods and didn't have a place to live in the summer, so I was at my parents' place and they had cable. It was pleasant to wake up every day for 2 weeks and just watch the scenery of France slowly pass by, and wait for the buildup of the stage finish. The tactics of cycling immediately fascinated me, it was so unlike any other sport.
I had no idea who Virenque or Zabel were, that there was a history of the race, and a whole rest of the season. I knew who Armstrong was, of course (and already disliked him, although I was at the edge of my seat the stage he pipped Kloden at the line), but not much else. The Tour caught me up. In 2005 I was taking a french language program in Quebec and didn't have TV and would follow online text updates every day obsessively. 2006 I was back home and taped every stage to bring to show my friends, I would often watch them twice. It was that winter that I discovered an online, year-by-year history of the Tour (no longer available for free) that gave me context around the cycling season. I read it twice, and mention of other races and historical achievements made me look for year-round coverage, which is when I started following cyclingnews. Now I'm hooked, I've been to see stages of the Tour in 2007 and this year, but the Tour is just a small part of the breadth of the cycling season, and I'm growing to appreciate the rest of the season more than the mainstream main event TdF every year. But it will always remain what got me into cycling.