Examples of getting RS232 serial ports up and running for various Microchip PIC microcontrollers.
Bootloader for Microchip PIC 18Fx52 including the PIC18F252 and PIC18F452.
Bootloader for PIC18F1320
Bootloader for Microchip PIC16F87x and PIC16F87xA.
Connect a USB cable to a PIC18F4550, add capacitor and crystal, and you have a COMx serial port.