Hi,
My first Linux distribution was Mandrake.
I worked on Solaris8 initially (my first *nix like OS) and I found it very annoying where everything need to do with command line :).
I wrote down some of the very frequent commands and keep repeating every-time.
Funny thing is for the long time..I even didn't know the meaning of most of the commands and their flags. I used to use them just because my mentor told me that for some specific tasks you need to run this command or so. 
Presently, I work on HP-UX, RHEL and Cygwin (at home).
My first was Ubuntu 5.04, introduction to linux / unix world (never seen a cli before)
Today i'm using Debian on my home machines (minimal install, currently looking at gnome3), and on my media machine also minimal install with X and XBMC.
I was pleasantly surprised with the quality of XBMC, a great product.
Work : HPUX, RHEL and Solaris.
Redhat and it still is.
Hi Folks,
First introduction to unix was CTIX (Convergent Technology) and then NDIX (Norsk Data), way back when I was an engineer in 1983.
First introduction to Linux was in 1993, when I tried to install kernel 0.97 on a Dell - 76 X 5.25 floppies and couldn't get it working so gave up for about a year and installed one of the very first versions of Caldera on the same machine some months later.
With an Adaptec 1540 Scsi card, 2x512Mb Hitachi Scsi HDD and a 525Mb QIC tape - used a file server.
This server ran without a reboot until just after the millenium when it was scrapped!
I've just installed Solaris 11 on one of our x86 boxes and am about to do the same on our test M4000 and T5220 before we start work on the bigger MX000 boxes - talk about "pointy clicky" - sheeeeeh!
Dave
Back when I was doing a CSAI degree, in about 94-5, I remember I guy I knew sitting at the next door Solaris workstation, with a huge box of departmental 3.5 floppy disks, copying some version of Linux onto them to install on his own PC later. He told me about this great project to bring UNIX to the masses and it was called Linux - it was the first time I'd heard of it and it looked like a major hassle. 
PS. My first install was with a CD-ROM, pheww.
RedHat 4.1 and
Slackware 3.2.
Tried both at the same time, while trying to configure an US Robotics modem!
knoppix - ubuntu - redhat
Redhat 4.2
I remember convincing my mom to drive me and my friend to CompUSA so we could pitch in to buy a copy. Neither of us had a CD burner at the time to download and burn our own.
My first was Ubuntu but I didnt do anything serious with it. For more then a month now I am working with custom Linux, made in ltib for an arm board.
I started with Slackware 7.1 in 2004
Unix: Sys V R2
Linux: Slackware 2.1
BSD: 4.3BSD
Linux - Ubuntu 8*
I never really did anything with it other than be like "holy crap I don't know how to do anything!"
----
Unix - Solaris
Use it for work now. Do KSH scripting and job scheduling.