BackOffice Small Business Server (SBS) contains a tool named Modem Sharing. You can administer Modem Sharing in Windows, or you can use the Netmodem.exe tool at a command prompt.
http://support.microsoft.com/kb/224504

When a Microsoft Small Business Server client attempts to perform a modem sharing function, it may define the user as "user-mode programmer" and when opening a remote COM port to ...
http://support.microsoft.com/kb/193529

A Modem Sharing Device (MSD), also commonly known as a Line Sharing Device (LSD), modem sharer, or line sharer, allows multiple devices to share a serial connection.
http://en.wikipedia.org/wiki/Modem_Sharing_Device

SmallNetBuilder.com Info about Wireless, Cable, DSL, routers, how-to's and much more. Run by Tim Higgins, this site has it all and is a must visit.
http://www.cablemodeminfo.com/sharebasicsx.html-ssi

Cable Modem Sharing ... Cable modems may be the most readily available broadband internet ...
http://www.homenethelp.com/sharing/cable-modem.asp

home networking - share a 56k modem or v90 modem internet connection ... Dial-up modems might be slow but they are not going away any time soon.
http://www.homenethelp.com/sharing/modem.asp

... modem sharing) 4 ports, 1 or 2 phone lines, automatic or semi-automatic operation
http://www.commandcommunications.net/modem_sharing/modem_sharing.html

20 + computers, 1 modem? No problem. Just designate one workstation to handle all of the communications. Whenever a user adds a new transaction, the modem server will ...
http://www.realsol.com/modem21.htm

I want to set up my daughters PC so that she can share one 56K USB modem which is connected to my PC. Is it possible to share the modem via a ROUTER ... I want to set up my ...
http://www.windowsbbs.com/networking/21032-modem-sharing.html

Modem Sharing - java scripts and applets. Free javascript downloads available from a variety of different categories.
http://www.javaarchives.com/modem_sharing.html

From: "Michael Creed Jr." To: Subject: Modem sharing; Date: Fri, 2 May 2003 18:19:00 -0400
http://www.redhat.com/archives/shrike-list/2003-May/msg00150.html

From: Charles Galpin To: redhat-list redhat com; Subject: modem sharing; Date: Sun, 21 Mar 1999 16:36:33 -0500 (EST)
http://www.redhat.com/archives/redhat-list/1999-March/msg03223.html

Hello everyone, I have a three computers networked together. They are: 1. PIII 800MHz, running Mepis, with a USB printer and a dial-up Netcomm modem;
http://www.mepis.org/node/7200

Modem Sharing. One approach to sharing multiple computers on one DSL connection is to use an Ethernet Router. The router will automatically create IP addresses ...
http://www.surfcitynetworks.com/support_modemsharing.htm

Revision History; Revision v1.12: 2001-08-22: Revised by: gjf: Corrected author's email: Revision v1.11: 2001-07-12: Revised by: aeg: Converted to DocBook SGML
http://www.faqs.org/docs/Linux-mini/Linux-Modem-Sharing.html

CC Proxy, an easy-to-use modem sharing software, supports Modem sharing, DSL connection sharing, broadband sharing, Satellite sharing, wireless sharing, cable modem sharing and ...
http://www.youngzsoft.net/ccproxy/connections.htm

Home | Fax Software Store - Fax software for Windows that turn your PC into a complete fax messaging system with Caller ID, answering machine, and voice mail.
http://www.faxcall.com/soft/modem-sharing.htm

Revision History; Revision v1.12: 2001-08-22: Revised by: gjf: Corrected author's email: Revision v1.11: 2001-07-12: Revised by: aeg: Converted to DocBook SGML
http://tldp.org/HOWTO/Linux-Modem-Sharing/index.html

NetModem Modem Pooling software for Windows
http://netmodem.com/

DEKSI Modem Pooling; PPPshar Lite; PPPshar Pro; GateWall; Proxy-Pro Professional GateKeeper; ... Modem Sharing Software Store. Powerful and feature rich modem pooling/sharing ...
http://www.ivrsoft.com/resources/modem-sharing.html