Hacker News Reader

Huh, go figure. It really took off as the home for artisanal techie websites:

(Beattie credits evocative short name, stable British administration, lots of available short and English word domains.)

Yup, nothing to do with APIs though.

Another clever new-ish one is .ac, but it's more expensive than the already expensive .io.

.io domains are very popular in a ton of different areas, though!