This is a project I've been playing around with over the last two years. It implements most of the functionality itself, like font rendering, javascript, images etc.
It does a decent job at rendering very basic pages, but of course there is an infinite amount of work left to be done, as can be seen in the ACID1 rendering here (:
And of course, contributions of any kind are welcome. (except backdoors. Please don't add backdoors.)
There are some issues listed in the repository, but everyone is free to work on what they want.
Repository Link: https://github.com/Wuelle/Stormlicht (~60k LoC)
Feel free to ask me about any questions you might have, or any issues you encounter!