One nice thing about Proton+ is in the forum, Les the compiler author occasionally posts misc. PDS code. (In addition to helping out on the forum when needed.) For instance, he's posted a full Space Invaders game that works with the Crownhill development board... which is modeled in the VSM simulator so you can play it right on your PC screen (or the actual development board).

He's also posted code to use as a serial buffer for the hardware usart, so it will receive data in the background, and fill it in when you get around to using a hserin command. More examples are speech decompression routines, and a full .wav file player design with CF FAT and audio out routines.

These are just a few examples. Some of them can easily be ported to PBP; others may take some work.