Google Open-Sources Gumbo: C Library for Parsing HTML5
I would be quite interested in Gumbo as the backend to the awesome pure Python but otherwise rather-slow https://github.com/html5lib/html5lib-python, which actually has great whitelisting/cleaning facilities but is easily an order of magnitude slower than lxml's more limited clean_html.PyPy JIT and html5lib is about 8x faster as it is cpython.