Python has been ported to the web browser at pythonfiddle.com. Python Fiddle can import snippets of code that you are reading on a web page and run them in the browser. It supports a few popular libraries.
Another common usage is to post code on the site to allow other people to play around with it. Also, it can be used to demonstrate a working program. -- http://mail.python.org/mailman/listinfo/python-list
