Aside from doing semi-perverse things with my email retrieval system, one of my most recent technical/digital obsessions has been with a X11-based window manager called awesome. It's a tiling window manager, and it's designed to decrease reliance on the mouse for most computer interaction/system navigation purposes.
Unless you're in the choir, your first question is probably "What's a tiling window manager?" Basically the idea is that awesome takes your entire screen and divides all of it into windows that are a lot like the windows that OS X, Windows, GNOME, and KDE users are the same. Awesome also has the possibility for what it calls "tags," but which are akin to virtual desktops (and I think of as slates) which make it possible to have a great number of windows open and accessible which maximizes screen efficiency and multi-tasking while minimizing distractions and squinting.
The second question you might have, given the prevalence of the mouse-pointer paradigm in computing lo these 30 years, why would you want a system that's not dependent on the mouse? Long time readers of the 'blag might remember some blogging I did earlier this year about the second coming of the command line interface. The basic idea is that the more you can avoid switching between the mouse and the keyboard, the more efficient you can be. Keystrokes take fractions of seconds, mouse clicks take many seconds, and this adds up. The more complex idea is that text-based environments tend to be more scriptable than GUIs and coded more efficiently with less mess in between you and your data/task. After all, coding visual effects into your text/word processing application is probably a sign that someone is doing their job horribly wrong.
One of my largest complaints about using GNOME is that it's terribly inefficient with regards to how it uses screen space. Maybe this is the symptom of using a laptop and not having a lot of space to go around, but most applications don't need a menu bar at they top of every window, and a status bar at the bottom of every window, and a nice 5 pixel border. I want to use my computer to read and write words, not look at window padding (I suppose I should gripe about GNOME at some point, this is an entry onto itself.) Awesome fixes this problem.
I'm not jumping in to Awesome full time, but I am starting to use it more and learn about it's subtleties, and hopefully I'll be able to contribute to the documentation of the project (it needs something at any rate). For a long time I've flirted with Linux, but haven't ever really felt that it offered something that I couldn't get with OS X, and this changes that pretty significantly.
One of the things that I need to do first is explore Linux equivalents to my remaining OS X-only apps. The most crucial is the news reader, I'm a big fan of NetNewsWire, and I've never used a news reader which can top it. As it turns out, between vim and Cream, I'm pretty set in the text editor department (though I need to port over the most important of my scripts and snippets to vim), and although Adium is a port of Pidgin, using Pidgin is painful by comparison, particularly in awesome.
But I have time. I'm doing this becasue it's interesting interested and weirdly enough, it's kind of fun.
That's my story and I'm sticking to it, I'll be posting more on the subject as I learn more.