Virtual Serial Port Driver allows creating virtual serial port pairs on a PC.
Serial Port Software
Serial Port Splitter grants simultaneous access to a COM port from several apps.
A program to help developers generate serial numbers for applications.
Displays, logs and analyzes all serial port activity in a system.
This app allows you to check the flow of data through a computer's COM ports.
HHD Software, Ltd.
It allows you to create virtual serial ports and emulate their behavior.