ReuterSport.com

Virtual Serial Port ActiveX Control
Allows application to create custom additional virtual serial port in system and fully control it. Created virtual serial ports looks like real serial ports for other Windows applications. [Commercial]
www.mks.zp.ua/

Serial Port Mapper : Program allows you to map any serial ports
Program allows you to map any serial ports to any other serial ports.
www.serial-port-mapper.com/

Universal Serial Port Python Library
A multi-platform pure-Python module to access serial ports, which currently works on Linux and Windows. [Open Source, GPL]
balder.prohosting.com/

Mac Serial Port Interfacing
Tips for interfacing a Mac serial port to RS-232 lab equipment.
francis.courtois.free.fr/

libserial -- simple serial port programming API
The linSerial class provides a simple, basic framework for managing a serial port. The design of this class is focused on making serial port easy to use, hiding the complexity of the full Linux/Unix termios interface. The goal is to make writing programs for modems, serial printers and other serial-attached devices easy for the novice serial port programmer
linas.org/

Virtual Serial Port SDK
Create and manage virtual serial ports from .NET and ActiveX.
franson.com/

Unix Serial Port Resources
Lots of resources on configuring serial/modem communications.
www.stokely.com/

Serial Port Sniffer ActiveX Control
Serial Port Sniffer is a powerful advanced ActiveX Control that allows your application to sniff (fully monitor and edit data flows) serial port in your system.
www.serial-port-communication.com/

Virtual Serial Port Kit
Program creates pairs of virtual serial ports connected virtually to each other.
www.virtual-serial-port.com/

Serial Port Monitor
Professional application for RS232/422/485 COM ports monitoring. It monitors, displays, logs and analyzes all serial port activity in a system, tracks down problems in system or application configurations and processes.
www.eltima.com/