I discovered MAME around the beginning of 1998 or so. I had already purchased Microsoft's "Return of Arcade" and William's "Arcade Classics" collections, but with MAME I was able to play practically every game - even the more obscure ones - that I remembered and loved as a kid. I downloaded and played a ton of ROMs for MAME and had a blast. It pretty much goes without saying that a lot of the newer games that come out nowadays are beautiful to look at, but few of them have that suck-you-in gameplay that could be found in those early classics.
I don't how it happened - it was one of those blind internet wanderings - but one day in June 1999 I stumbled upon Shadow's PC Arcade* page. I couldn't believe what this guy had done: he had built an actual upright arcade cabinet which housed a PC that was running his emulators, and it was all interfaced through genuine arcade controls! I had never seen anyone who had done such a thing! Man, I was hooked. Forgoing sleep that night, I read everything that I could find on his page, followed all of his links, followed all of those links, and so on.
I finally came upon the motherlode: the Build Your Own Arcade Controls FAQ page. Would you believe that there exists an entire grouping of people who have built their own cabinets? Neither did I, but they do exist. It was there that I found links to dozens of people's websites featuring hand-built or converted cabinets, as well as several instructions and tips that anyone would need to get their own arcade project off the ground. "Holy crap," I thought, "I might actually be able to pull this off!"
The seed had been planted...
*Sadly, Shadow's PC Arcade page has since disappeared, current whereabouts unknown. I'm keeping the last known URL up here though for historical reference.