Quite recently the matplotlib web site was redone, with considerable improvements in documentation. If you are interested in matplotlib plotting, check out http://matplotlib.sourceforge.net/. The "gallery" link has a disorderly collection of examples with source code, so you can get an idea of the range of things mpl can do. Some of the examples use features that were added very recently, possibly even since the last release; mpl is still developing quite fast.
And on a related topic, as a reminder: numpy documentation is available at http://scipy.org/Documentation.
If you want to use numpy and matplotlib, then it is a good idea to subscribe to the mailing lists:
You might want to peek into the archives to get a sense of the character of these lists.