huxley
Huxley is a test-like system for catching visual regressions in Web applications. It watches you browse, takes screenshots, and tells you when they change.
Project Source: https://github.com/facebook/huxley

sparkup
Sparkup lets you write HTML code faster. You can write HTML in a CSS-like syntax, and have Sparkup handle the expansion to full HTML code.
Project Source: https://github.com/rstacruz/sparkup
Online Demo Address: https://github.com/rstacruz/sparkup

xhtml2pdf
HTML/CSS to PDF converter based on Python
Project Source: https://github.com/chrisglass/xhtml2pdf
Project Homepage: http://www.xhtml2pdf.com/

bleach
An easy, HTML5, whitelisting HTML sanitizer.
Project Source: https://github.com/jsocol/bleach
Project Documentation: https://github.com/jsocol/bleach

scrapely
Scrapely is a library for extracting structured data from HTML pages.
Project Source: https://github.com/scrapy/scrapely

mincss
Tool for finding out which CSS selectors you're NOT using.
Project Source: https://github.com/peterbe/mincss
Project Homepage: http://peterbe.github.io/mincss/

WebPutty
WebPutty is a simple CSS editing and hosting service that you can run on Google App Engine.
Project Source: https://github.com/FogCreek/WebPutty

webassets
Asset management for Python web development.
Project Source: https://github.com/miracle2k/webassets
Project Documentation: http://webassets.readthedocs.org/en/latest/script.html

html2text
Convert HTML to Markdown-formatted text.
Project Source: https://github.com/aaronsw/html2text
Project Homepage: http://www.aaronsw.com/2002/html2text/

anim_encoder
anim_encoder creates small JavaScript+HTML animations from a series on PNG images.
Project Source: https://github.com/sublimehq/anim_encoder

boom
Boom! is a simple command line tool to send some load to a web app.
Project Source: https://github.com/tarekziade/boom

WeasyPrint
WeasyPrint converts web documents (HTML with CSS, SVG, ...) to PDF.
Project Source: https://github.com/Kozea/WeasyPrint
Project Homepage: http://weasyprint.org/

centrifuge
Simple real-time messaging in web applications.
Project Source: https://github.com/FZambia/centrifuge

pyjs
pyjs is a Rich Internet Application (RIA) Development Platform for both Web and Desktop.
Project Source: https://github.com/pyjs/pyjs
Project Homepage: http://pyjs.org/