In terms of cycling, my story is probably very common. Dropped off after getting a drivers license. Went to nothing in college. Job/marriage/kids got in the way and let myself slide. Thought to myself, I really liked cycling when I was a kid, I'll try that. Bought a used bike to dip my toe in the sport again. And it stuck for the last dozen+ years.
Before I bought the used bike, I went to the LBS and had my eyes opened. Really light bikes from what I remembered. "Fancy" shifting. Cool stuff.
But learning the depth of cycling came from,
1. Sheldon Brown
2. Bike Forums
3. Classic Rendezvous
4. A large variety of blogs where I have had the pleasure of building personal relationships with the authors
My oversight by not giving credit to the late Sheldon Brown. I thought I knew something about bikes, until I didn't, and then I found Sheldon's site. OK, now knowing my ignorance, I began to attempt to redress that - so here I am.