WebPd aims to allow a subset of Pure Data patches to run in the browser without plugins (only firefox4 supports writable audio at the moment). Right now the focus is on dsp~ objects, to enable you to mock up dsp engines in Pd, put them on the web, and control them with Javascript.

Documentation and tests/examples: http://mccormick.cx/dev/webpd/

There is a low-frequency mailing list here: http://groups.google.com/group/web-pure-data

Here is a cool page demonstrating a GUI for WebPd: http://webpuredata.org/

A good tool for writing front-ends is here: http://processingjs.org/

WebPd is licensed under the terms of the AGPLv3. See the file COPYING for details.