My first distribution, and first introduction to UNIX-like systems in general, was Mandrake. I got it because I could buy the disk at Office Depot or some-such. This was early 2001-ish. Mandrake Linux doesn't even exist anymore, it became Mandriva.
I did the full install and got with it a ridiculous number of programs and a nice GUI for me to web-browse in. I didn't learn much about Linux or shell programming or shell commands or much at all until the day came I wanted to hook up a printer and couldn't. Building myself a new kernel made the printer work, but violated some dependency thing, and the RPM-based installer refused to do anything at all, ever again.
My next one was Gentoo and I had more luck with it.