ictfax - ICTFAX is web based and open source Fax software, It is multi users and suitable to offer online Fax services, including Email to Fax, Fax to Email and Web to Fax. ICTFAX application support FoIP, T38 and G.711 pass through faxing also PSTN fax.
faxjar - Send fax online. No registration required.
HylaFAX - HylaFAX Open Source is designed around a client-server architecture. Fax modems may reside on a single machine on a network and clients can submit an...
GotFreeFax - Send Free Fax Online to the U.S. and Canada.
ActFax - ActFax by ActFax Communication-Software GmbH - Fax Server and Email Software for Windows, Terminal Server, Citrix and Unix - ActiveFax Server
vFax - Get a virtual fax number for as low as $2.99 per month and 3.0 cents per minute