Protovis

Protovis is a visualization toolkit for JavaScript using the canvas element. It takes a graphical approach to data visualization, composing custom views of data with simple graphical primitives like bars and dots.

code: protovis.js
doc: http://vis.stanford.edu/protovis/api/
demos: http://vis.stanford.edu/protovis/ex/
research paper: protovis.pdf

license: BSD
currently only works on FireFox 3, planning support for Chrome and Safari 4.

my favorite example: Job Voyager (open in FireFox 3)