Wordcloud is a project mainly written in Python, it's free.
My submission to the "Agile Open Cup" challenge at Agile Open France 2011, implemented in Python using the Pylons web framework.
Make a Python virtual environment::
virtualenv --no-site-packages .
source bin/activate
Install dependencies in the virtualenv::
pip install -r requirements.txt
Start the server::
paster serve development.ini