Short bio: Computer Scientist, FOSS supporter (read more)
Tux Machines (TM)-specific
I think that the first "packaged" Linux distribution that I ever tried was Slackware Linux. I haven't had much to do with Slackware in quite a few years, though. When I saw the release announcement for Slackware Linux 13.0, I happened to be working on MMS (my MultibootMiniServer), and I thought it might be interesting to try it on there. Then I read the release notes, and saw that it had a new release of Xfce, and that made the decision for me. So I downloaded and burned the DVD image, and booted it up.
Let me say that loud and clear at the start. Slackware Linux is not a distribution for beginners, or even casual users. Don't get me wrong, it is a very good and very solid distribution, but it is for big boys and girls who know what they are doing with Linux installation, setup and administration. There is no LiveCD, only the Installation DVD. There is no "Graphical Installation Process", only the (perfectly adequate) ASCII/text installation program. So if you go into this thinking you are going to do something like installing Ubuntu, Mandriva, or whatever your favorite desktop/graphical Linux distribution might be, you are likely to come out of it shell-shocked.