A desktop chat client that time-traveled from 1998 and learned to function in modern society.
The Qt style engine built for Ripcord. Available for free as open source.
A single-file no-dependencies C99 library for doing 2D UI stacking box layouts. The kids call this "flexbox," apparently.
ORCΛ (C99)
A C99 version of the ORCΛ esoteric live programming environment and language. Includes a terminal-based IDE, IO with MIDI/OSC/UDP, time-travel debugging environment with multiple undo, and a no-dependencies core virtual machine which can easily be embedded into other software.