I am the author of these projects:
- HTMLDecor - Why should you be merging your real content with your shared page template - that is, your site decor - on the server? Do it in the browser and history.pushState() comes for free.
- XBLUI - XML Binding Language User Interface enhancements
- SLAB - Standards Layer for APIs in Browsers
I have also contributed to MathJax - beautiful math in all browsers - which is used by math.stackexchange.com.