At its essence, Snow Crash introduced me to the idea of hacking. That is, hacking in the abstract sense of using knowledge about the inner workings of things to influence the world. At the time, I didn't know anything about software yet. Even though the main hero of the book is a master hacker and part of the book plays out in cyber space, it never really talks about the act of writing code. I would learn about that later.
Snow Crash was my red pill. Re-reading it today, after having been a professional software engineer for a number of years, I can't overstate how influential this book has been in my life. It instilled in me the desire to understand the deep structures of things. And with that, the ability to influence and create the world around me. It set me on the path to becoming who I am today.
Snow Crash also served as my introduction to modern utopian cyberpunk. Even though I spent my youth playing video games and reading bad sci-fi, I still remember Snow Crash as my formal introduction to cyber space, virtual avatars, megacorporations, and light cycle races. And it told of the awesome power of reason.
My second favorite Stephenson is Zodiac, strangely.