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Any sufficiently advanced technology is indistinguishable from magic.
- Arthur C. Clarke
For most of the 'static' pages, horizon-nigh.org runs a custom content-management system, which I call Nuage. This is built on top of the Symfony web framework for PHP, which I highly recommend. Data is stored in an SQLite database, accessed through the Doctrine ORM. (No need for a 'real' database for something this small, but for bigger projects, I like PostgreSQL.)
The module that powers the Photos section, I also wrote myself, and I have packaged it as a Symfony plugin called hnPhotoAlbumPlugin, which you can download and use on your own Symfony-powered web site.
All of this is is hosted by NearlyFreeSpeech.net, which provides top-notch hosting for an insanely little amount of money. All of their services are custom-built and their attention to detail is like nothing I've ever seen. I don't benefit in any way by mentioning this; just very satisfied with their services.
The Tumblelog section is powered and hosted by Tumblr, with comments functionality provided by Intense Debate.
I develop on a Mac, using Panic's Coda, which is basically 'Xcode for the web'. I use Git and GitX for versioning and deployment, which is a breath of fresh air after years of fighting with Subversion.
I test in WebKit and Gecko to make sure my code is valid. Because Internet Explorer is not compatible with web standards, it takes an unusual amount of extra effort to ensure compatibility - thus, although I test in IE in my professional work, I do not do so for my personal site, and therefore IE may not work correctly with this web site.
My friends have informed me that my header graphic is too large; unfortunately, I like it too much.