Well the first time I used a Mac was when I used my Dad's G3 to play bugdom. I'm not sure which year it was but I think it was early 2000s. It was running OS 9 and was a refurb, I think. I'm not sure about it anyway but I fondly remember playing bugdom. That was one epic game.
I also used some G3s at school (around 2003, 2004) and used an app called "Amazing Animation". I was pretty good at it and I enjoyed using it

shame I didn't become interested in Macs sooner... I guess it was because I had Windows XP at home which I was not only more familiar with, but I thought it looked better than OS 9.
My Dad then bought an iBook G4 that I used once or twice. I thought I deleted iMovie because I accidentally removed it from the dock. Oops. I've never actually told him but I guess that since I didn't delete it properly, it should be there still xD Anyway, I used MSN on it and didn't like the MSN client as it sucked - which is why I now use Adium

Finally, I used some Mac Minis at school with Comic Life, which was fun. To my annoyance, Comic Life is not included on new Macs... WHY!? It was one of the things I loved about the Mini I used (ah well, I'll buy it one day).
Oddly, the day my iMac arrived, I saw that my school had bought some older 17" iMacs (it was September 07) and it made me want mine so badly... then when I got home, there it was! haha. It heard my prayers!
So yeah, that's my story of my introduction to Apple. I think I used my friend's iPod Nano briefly before-hand too, but that doesn't really count.