Programming
Okay, I may as well get it out there: I'm a computer dork. There, I said it. I'm not nearly as bad as I was a few years ago, when I frequently stayed at home on a Friday or Saturday night and read about programming or actually wrote code. My favorite languages are perl, php, and I have recently grown quite fond of css.
Platforms
It wasn't until I got to college that I really started learning anything about computers. I had a Gateway 2000 pc running Windows 95 (uh oh, I'm dating myself). One of the assistant swimming coaches turned me on to Linux and the beauty of html. I played around with both throughout my time in college, but I never really got to be all that great with Linux. In my job as a research technician I got to be more comfortable with the platform. After a few years our lab purchased some hardware that only interfaced with Macs, so I got a mac. Though I was reluctant at first, I've totally become a Mac person. In my opinion Macs have stability that approaches Linux (not quite there), but so many good features. The gui interfaces are good enough to steer me away from working so much in the command line, and with X11, I can still go back to the familiar command line stuff whenever I want.

Software comes with some tradeoffs, of course. On one hand some of the free Unix based stuff is harder to install on macs, or doesn't work as smoothly, but there are loads more programs written by people that actually get paid to program, so they actually finish the projects. I think open source is a beautiful thing, and there are loads of outstanding programmers that write open source code, but there are also tons of unfinished products. Anyways, Macs rock, I just wish I could afford one for myself (or any nice computer for that matter).
Favorite Software
Given that I am moderately obsessed with photography, I have opinions about photo software. This is one place where I think open source has done a remarkable job. I think gimp is a truly outstanding graphics manipulation program. To be fair, I have not used photoshop that much, and I know it has some great features, but I love practically everything about gimp. I only wish there was a free vectorized program out there analagous to Illustrator (let me know if you are aware of a good one!).

When I program, I use emacs almost exclusively. Of course there are other powerful text editors out there, but emacs is the one that I know the keyboard shortcuts for, and it's just so powerful.