Nick has produced (or is in the middle of producing) the following things that may be of general interest to other developers. If that’s you, feel free to use what you see. Source for most items is made available under the BSD license.
Drag: a JavaScript drag-and-drop engine, with collision detection and arbitrary constraints, that is shockingly cross-browser compatible.
Dynamic Rasterization with Scripted SVG: a simple method for leveraging your favorite web development language and your favorite vector illustration package to produce jpeg/png/gif images that can be changed as easily as updating a stylesheet.
Catgut: a lightweight, highly extensible markdown engine (using a simple, intuitive syntax similar to many wikis) for incorporation in content management systems.
User path visualization: graphical flowcharts of customer's usage patterns, generated on the fly from shopping cart site statistics.