There is a script for converting pcb files directly into
HPGL for printing.  It does not support all of pcb's features.
There is a tcl script that converts Tango netlist format
into a pcb compatible netlist format.  It was written by Ingo Cyliax.
There's a tool to merge several PCB generated PostScript files
into a single one. Check the code for details.
There is a gzipped tar file containing a program to help you
use the MUCS PCB auto router if you want to.

