Chris Holden made a font library for a Nokia 5110 display using a PIC microcontroller and Oshonsoft. He writes:
Having left the 1980’s behind, we decided to write our own “libraries” to write text onto the Nokia 5100 display, using a PIC microcontroller. The code below was written for a 16F877a (because it was the first chip we found already on a breadboard, with a programming header connected) but would work equally well on any PIC microcontroller with enough RAM for the font table.