Principles of Uncertainty — probability and statistics textbook, for maths students to build up to understanding Bayesian reasoning.
Playable Archaeology: An Interview with the Telehacks Anonymous Creator (Andy Baio) — The inspiration was my son. I had shown him the old movies Hackers, Wargames, and Colossus: The Forbin Project and he really liked them. After seeing Hackers and Wargames, he really wanted to start hacking stuff on his own. I’d taught him some programming, but I didn’t want him doing any actual hacking, so I decided to make a simulation so he could telnet to hosts, hack them, and get the feel of it, but safely. (Andy was the interviewer, not the creator)
Responsive Data Tables — CSS ways to reformat data tables if the screen width is inadequate for the default table layout. (via Keith Bolland)