WordPress powers this site. My tumblelog style of blogging would be much more difficult without its extensibility.
More specifically: the tumblelogging features on this site are enabled by a custom-written theme and a plugin that makes it easy to vary the basic “template” for a post based on custom field data.
I also post reviews, mostly of video games; these use the hReview microformat.
Slicehost is my web host. Cheap, fast, developer-friendly VPS hosting.