The first Linux distro I had ever touched was some Finnish-made one... SOT Linux, I think...
Back in 2005, I installed Ubuntu and dualbooted it along with XP, used it for a few months until I didn't need it anymore (mainly I was just using it to play America's Army with much higher framerates

). I also experimented with things and so with it.
Just a few weeks ago I had to use Knoppix for 5 days while troubleshooting a certain hard disk problem. I had fun.