I listened to my first MP3 ever (Creed's "Higher") in 1999 on Winamp. It really whipped the South American camelid's posterior. Dang. I'm old.
After years of listening to Adlib MIDI soundtracks on the computer, I was absolutely blown away to be hearing “Yesterday” by the Beatles coming out of the speakers. I played that tiny little file (not a whole CD!) countless times on repeat. Just unbelievable that such a thing could be coming from a tiny (relatively) little file.
I also remember being so thrilled to be able to store several MP3's on my 64mb Sharp Zaurus SL-5600.