Programming
At the moment I'm mostly interested in Scheme and Ruby, plus JavaScript combined with either HTML/CSS or SVG. I also know Perl, C, Java, and a number of other languages. Perl still fascinates me a lot, and I'm using it for this Web site, but I'm not doing any really serious coding in Perl at the moment.I think that Scheme is steadily becoming my favorite language. It's powerful, expressive, and fast. Plus it uses recursion a lot, and I tend to think well in recursive terms.
The programming language I use professionally now is Ruby. It has a lot of features in common with Scheme, so it's fun for me to use. I've used the Rails framework (written in Ruby) for a number of projects, but I'm now strongly considering a move to a different Ruby framework, maybe Merb.
I'm very interested in functional programming. For people with an interest in Perl, I recommend the book Higher-Order Perl, by Mark Dominus. It'll help hone your Perl skills and teach a lot about practical functional-style programming.
Another thing I like in a programming language is interactivity. Programming languages like Ruby and Lisp allow you to load code you've written and type commands in the language at an interactive shell, and see the results. It's great for development and testing. In fact, an interactive shell has become something of a sine qua non for me. The excellent Firebug extension for Firefox provides such a shell for JavaScript too, which is probably why my interest in JavaScript is higher now than it used to be.
I use the vim text editor for everything, programming and prose. For now I've settled on Debian-based Linux to do pretty much everything on. I use Ubuntu for a desktop OS both at home and at work. For servers I use Debian.