smalldacrt. A Divide and Conquer RayTracer as described by Benjamin Mora and
with an implementation based on smallpt, a path tracer be Kevin Beason. (But
written slightly more human readable)

Compile ./make smalldacrt
Usage: ./small 16 && xv image.ppm

smallcone. A rayTracer using a cone ray hierarchy as described by Roger et
al. (2007) and with an implementation based on smallpt, a path tracer by
Kevin Beason.  (But written slightly more human readable)

Compile ./make smallcone
Usage: ./small 16 && xv image.ppm