The Hexo static blogging engine gets an admin UI
I recently switched from ghost to hexo, and the biggest thing missing for me was the editor interface. So I made one. Currently, it's mostly a clone of the Ghost interface, but I have some ideas for making it even more awesome.
Photon Ray Tracing
A few months ago I saw @scanlime's "Zen Photon Garden" on hacker news, and was really impressed. In short, you draw walls/mirrors with your mouse, and it ray-traces light from a central source. Very beautiful and "zen". However, as a programmer, drawing lines by hand was far too inaccurate. So I forked it and added a scriptable interface for adding walls.