From the Sweet New Shiny Stuff dept.:
With Jetpack, we’re building upon our experience over the last four years empowering a community of more than 8,000 developers to produce more than 12,000 add-ons to imagine and build the next generation of the add-ons platform. We want to grow our community of developers by orders of magnitude through making add-on creation much more accessible, and yet more powerful by developing it as an extensible platform for innovation itself. Many useful Jetpack Feature’s can be written in under a dozen lines of code.

Specifically, Jetpack will be an exploration in using Web technologies to enhance the browser (e.g. HTML, CSS and Javascript), with the goal of allowing anyone who can build a Web site to participate in making the Web a better place to work, communicate and play.

labs.mozilla.com