RS-232

Keith's RS-232 Library
Documentation with download.
http://www.ent.ohiou.edu/~welker/rs232/

Quick Reference
For RS485, RS422, RS232 and RS423.
http://www.rs485.com/rs485spec.html

RS-232 Diagnosis Tech Bulletin From Mike Sandman
RS-232 Serial Communications is not that hard.
http://www.sandman.com/rs232.html

The RS232 Standard
A tutorial with signal names and definitions.
http://www.camiresearch.com/Data_Com_Basics/RS232_standard.html

Serial/Rs-232 Interfacing
Detailed explanations on interfacing the serial port.
http://www.beyondlogic.org/serial/serial.htm