I have been doing some work to extend Google's Native Client  to support dynamic linking . For those who haven't heard of it, Native Client is a sandboxing system for running a subset of x86 code. It is proposed as a way of running native code inside web apps.
One of my aims has been to get CPython working in the web browser under Native Client without having to modify CPython.
I recently got to the point where modules from the Python standard library are importable under Native Client, including (as a demonstration) the Sqlite extension module. Sqlite also requires no modification - it builds straight from the Debian package.
I've written a simple REPL to demonstrate Python running in the browser. There are some screenshots on my blog . I haven't implemented accessing the DOM from Python yet - that's another project for later. :-)