audio:
stb_audio_mixer.h
Low-latency audio mixing, plus optional direct-sound interface (insufficiently documented); forum thread
stb_synth.h
Simple but flexible software synthesizer -- note canonical waveforms are not properly band-limited (for best quality you'd want to generate at a higher audio rate and then filter)
stb_synth_test.cpp
Demo of audio libraries.
misc:
stb_pixel32.h
Alpha-blending, bilinear sampling of 32-bit RGBA pixels
stb_file.h
Weird file-processing routines deleted from stb.h
stb.h:
stb_h.html
Documentation for stb.h
stb.c
Unit tests for stb.h.
stb_stua.html
Documentation for STB_STUA, found in stb.h