Bokeh is an implementation of Grammar of Graphics for Python, that also supports the customized rendering flexibility of Protovis and d3. Although it is a Python library, its primary output backend is HTML5 Canvas.
There are many excellent plotting packages for Python, but they generally do not optimize for the particular needs of statistical plotting (easy faceting, bulk application of aesthetic and visual parameters across categorical variables, pleasing default color palettes for categorical data, etc.). The goal of Bokeh is to provide a compelling Python equivalent of ggplot in R.
A related project is Pandas, whose DataFrame objects are directly used by Bokeh. Bokeh will also interface with the NDTable objects in Blaze.
Bokeh has a function-oriented interface that closely resembles ggplot. These functions can be used interactively from the Python prompt, or from within a script (a la Matplotlib). Behind the scenes, these functions construct a scenegraph and data transformation pipeline that consists of nodes which can export their state into JSON.
The JSON representation of the graphic is then embedded in an HTML document which also contains the Bokeh JS runtime. This runtime is built on a port of Protovis to HTML5 Canvas, and consists of some higher-level canned plot layouts built on top of the Protovis framework.
For the initial prototype, Bokeh is implemented as a wrapper on top of the Chaco plotting system, and displays its output using Chaco. This will change as we implement the Javascript/HTML backend.
You can install the following with easy_install, "pip install", or they may be available for your Linux system via the system package management. If you are using a distribution like the Enthought Python Distribution or Python(X,Y), then you already have them installed.
Bokeh was started in March 2012, and still remains in the experimental/prototype stage. It is under active development by contributors at Continuum Analytics, and with the recent award of a grant from DARPA, we are able to devote more resources into it, along with collaborators from Indiana University.