deeplinks.js allows people to easily link directly to any text selection on your website! It's designed to be easy-to-use, robust, and unintrusive.
MasterPiets is a very polished IDE and debugger for a very silly programming language. I appreciate the detailed attention to UX for such an esoteric language!
An explanation of some of the difficulties in private information retrieval, along with an interesting scheme to make using bloom filters more tenable.