Virtual Null Modem
Null-modem cable is basically used for communication of two RS-232 DTE devices with each other. To create null-modem connection between the devices you need to use two computers or two serial ports of a single computer connected with null-modem cable. ... Virtual null-modem allows user emulate virtual null modem connection and run the two applications simultaneously on the same computer. ... The most reliable way to create null-modem connection is using of virtual serial ports emulated by virtual serial port driver and null-modem cable.
http://www.virtual-null-modem.com/download/vnullmod20.exe - 1Mb - Download - Screenshot

Virtual Serial Port Kit
Virtual Serial Port Kit creates pairs of virtual serial ports in your system which are virtually connected to each other. Physical null modem cables are not required. You can connect any number of virtual port pairs. Virtual serial port pairs will look and work exactly like real hardware serial... Virtual Serial Port Kit is useful also for users which work with Windows applications using serial COM ports joined by null modem cable especially if those applications require more than one serial port pair.
http://www.virtual-serial-port.com/virtual-serial-port-kit.zip - 796Kb - Download - Screenshot

Virtual Serial Port Driver XP4.5
Virtual Serial Ports Driver XP creates two pure virtual serial ports in your system which are virtually connected to each other. For other Windows applications, virtual ports will be seen exactly as two real serial ports connected via null-modem cable. ... Virtual link between virtual serial ports is much faster then real null-modem cable connection and depends on your processor speed. ... The latest version with new manual and examples now supports full baudrate emulation. ... With user-friendly GUI and on-the-fly help of Virtual Serial Port Driver XP it's very easy to configure a virtual...
http://www.mks.zp.ua/vspdxpd.exe - 1Mb - Download - Screenshot

AlarIT Virtual Serial Driver (AVSD)
AlarIT Virtual Serial Driver is appointed for emulation of one, two or more (up to 200) serial streams. Hardware devices are not necessary. This product is based on Windows XP DDK and doesn't require using devices of other manufacturers. The whole product is created with the help of Microsoft... 0 with null-modem cable showed that they are practically identical. ... AlarIT Virtual Serial Driver realizes full emulation of Serial Port functions, connected with each other with the help of NULL-MODEM or full cable, including DTR, CTS, DSR, RTS.
http://www.alarit.com/downloads/products/avsd.zip - 448Kb - Download

Virtual Serial Port SDK
Using Virtual Serial Port SDK you can create a "new" serial port on your computer. This serial port is completely controlled by your application. Other 3rd party applications can connect to this serial port and believe it is a normal physical port. In this way you can emulate all kinds of... Samples in C#, VB. ... NET and VisualBasic 6. ... 0 are included. ... NET and ActiveX, on all Windows platforms Windows Mobile/Pocket PC, Windows XP/2k/NT and Windows ME/98. ... Virtual Serial Port SDK is available for .
http://franson.com/serialtools/SerialToolsSDK.zip - 2Mb - Download

Serial Port Terminal
Advanced Serial Port Terminal is a session-based, multi-purpose application that provides simple communication interface to connect to any serial port device (modem;fax;GPS;mouse;printer and so on). Whether you want to connect to remote computer using null-modem cable, send or receive various... Highly customizable interface lets you easily customize program interface to your taste and needs. ... Unlike other terminals you may not only send, but also receive and view data in hexadecimal format, switch between dump and terminal view modes, etc, which could be very useful for debugging and...
http://www.virtualserialport.com/download/serial_port_terminal.exe - 2Mb - Download - Screenshot

Multicom
Multicom is appointed for emulation of one, two or more (up to 200) serial streams. Hardware devices are not necessary. This product is based on Windows XP DDK and doesn't require using devices of other manufacturers. The whole product is created with the help of Microsoft tooling. ... Multicom realizes full emulation of Serial Port functions, connected with each other with the help of NULL-MODEM or full cable, including DTR, CTS, DSR, RTS. ... Multicomr can be interesting for software (for Windows Platforms) developers, who use external devices connected with computer by serial port.
http://www.intellidriver.com/downloads/products/multicom.zip - 448Kb - Download

AVSD
AVSD is appointed for emulation of one, two or more (up to 200) serial streams. Hardware devices are not necessary. This product is based on Windows XP DDK and doesn't require using devices of other manufacturers. The whole product is created with the help of Microsoft tooling. ... AVSD realizes full emulation of Serial Port functions, connected with each other with the help of NULL-MODEM or full cable, including DTR, CTS, DSR, RTS. ... AVSD can be interesting for software (for Windows Platforms) developers, who use external devices connected with computer by serial port.
http://www.miraclit.com/avsd.zip - 448Kb - Download

Advanced Virtual COM Port
Advanced Virtual COM Port is the first software of its kind which includes both local and network virtual COM port functions. It can share your real COM ports or it can create virtual COM ports and connect them with a virtual null-modem cable locally or through a TCP/IP network or the Internet. ... Virtual serial ports created by the program look and work the same way as real ones look and work. ... You can connect to a shared port and use it just like it is on your machine.
http://www.advancedvirtualcomport.com/files/AdvancedVirtualComPort.zip - 1Mb - Download - Screenshot

Virtual Serial Ports Driver XP
Virtual Serial Ports Driver (VSPD) creates two pure virtual serial ports in your system which are virtually connected to each other. For other Windows applications, virtual ports will be seen exactly as two real serial ports connected via null-modem cable. ... Of course, you can transfer files, other data or do whatever you want as it was real serial ports. ... With VSPD you can connect one application to another using virtual serial ports pair. ... This solution can be used, for example, for GPS simulation programs.
http://www.eltima.com/download/vspdxp.exe - 1Mb - Download - Screenshot