Overture is a JavaScript library that contains all the tools you need to build a slick, modern web app. It was originally built to power FastMail's awesome webmail.
To get started, check out the heavily commented Todo demo app in the examples folder, or use your browser web dev tools on the live demo at: http://overturejs.com/examples/Todo/.
You can find API documentation and download a pre-built copy of the library from http://overturejs.com.
Overture is MIT licensed. No animals were harmed in the making of this code.