OS : Dual boot of Ubuntu 6.06 Server (with the desktop stuff built on top.) and Windows XP SP2. My secondary computer (a celeron 566) runs Ubuntu Server with a desktop added with a mind towards fastness.
Skinnables : erm... not much, really; open/blackbox window manager (s consider that a 'shell') and themes for the two major window widget sets that roughly all match up. (There's a GTK+ theme which does all the GNOME apps, and a QT theme which does all the KDE apps.)
FLOSS software : lol!

Productivity tools :
- Firefox (1.5 because 2.0 is messy to get working from backports),
- Thunderbird w/ enigmail for mailing people about my plans for world domination.
- xterms by the dozen (i have an entire virtual desktop of just terminal windows.) In linux, the best ways to get things done often nvolve terminal windows (wget -r for the win!)
- Quanta Plus for PHP/XHTML web development, with the gubed PHP debugger.
- zim, which I cannot live without, for jotting down to-do lists, ideas, and brainstorming.
- KATE and tea for my text-editing needs - KATE for heavy lifting, tea for quick hacking. Both are leagues above most windows software and KATE is roughly analogous to OSX BBEdit. (that's high praise!)
- Inkscape for vector illustration, still trying to get a hang of the interface,
- Abiword for word processing, because OpenOffice.org sucks.
- LyX for TeX-based semantic document editing with inline math formulae (Rich problably understands why semantic > presentational - analogous to why stylesheets > font tags)
- Thunar file manager, which is a nice, clean explorer,exe like file browser (which of course doesn't suck as much.)
- maxima - a symbolic maths package which is a very good way to cheat on your maths homework, as well as solving differential equations and simultaneous systems on the side.
Non Productivity
- Amarok for music playing when I'm feeling indulgent, Rhythmbox/XMMS for when i don't have 300mb of ram to spare. (amarok is really really heavy handed on system resources, but the features are full justification.)
- gaim for MSN/Jabber, xterm+irssi+screen for IRC that never ever dies, even if you close the window.
- The Battle For Wesnoth, truly the most awesome open source strategy game ever. (comes for all platforms, go get it at wesnoth.org.)
- angband : a text-based hack-and-slash game that draws on Lord of The Rings - has many variants and had me truly addicted for a few weeks. (addicted to a *ascii display* game? It's very definitely possible.)
On my iBook (inherited

) I use some of the same apps, but mostly I get by with what OSX comes with plus what my brother lifted from the mac labs at JCU (isn't the OSX concept of programs as single files great?

) For text editing I often find myself using nano in a terminal, or TextWrangler (the free version of BBEdit, which is the single best reason to use a Mac ever.) I'm not really using it at the moment, but once i get back to university i'll probably stock it up with apps as my mobile needs see fit.
On windows, I use Dreamweaver 8 (only slightly better than Quanta really) and Photoshop CS2, the single best example of why open-source software has some catching up to do. I also use xplorer2, which is a very nice file browser. In the way of games, all I was playing was Neverwinter Nights (best RPG evarr) and Warcraft 3, by which I really mean DotA.