I'm using Linux right now. openSUSE 11.0, to be exact. I was even compiling a kernel module for my webcam while I was reading through this thread. I've used just about every distro out there. While this may not be the best, or my favorite even, it's one of the few newer distros that work perfectly. All of the newer ones have minor graphical glitches (Ubuntu, Fedora) or the X server doesn't run at all (Arch or FreeBSD, which is why I want to get back to one of them). I'm a computer engineering student, so I don't need a GUI. Give me a terminal and I'm just fine. My list of known languages is now up to 3 - Ada, C++, and Pep/8 assembly (although I'm doing very poorly at this last one).
I haven't really rebuilt computers from scratch, but I have ripped a few down fully and rebuilt them in working order (with but one or two spare screws). I've replaced my PSU, which is another interesting story. My new GPU had much higher power requirements than either of my dinky 110W supplies could provide, so I did the geeky thing and ran them in series, hard drive, disk drives, etc on one and CPU/mobo on the other.
I haven't overclocked and I've only dabbled with networking, but I can set up home networks if I have to.
I'll agree that the poll choices do not necessarily indicating skill. It's the same with everything else - what I find easy (command line in Linux and all that fun stuff) is different than what others find easy (overclocking or networking).
As a side note, do I use parentheses too much? It's an easy way to pass on information that doesn't fit in the sentence.