Quorum Call Conference Software
Quorum is software which runs as a phone conference server on any Windows PC. Callers dial into the server to join telephone conferences. Callers can connect to a conference call using either standard or VoIP lines on external telephone numbers or through an office phone system. ... The conference creator then gives this number to each conference participant. ... When the caller selects the option to create a new conference Quorum will assign and read back the unique and secure conference number.
http://www.audiochannel.net/software/quorum.zip - 947Kb - Download - Screenshot

Gizmo Project
Gizmo Project is a free Internet phone for your computer that lets users make crystal-clear free calls using the Internet. As easy to use as instant messaging, calls offer crystal-clear voice quality and PC-to-PC calls are always free. Calls to ordinary landlines and mobile phones are available... Gizmo Project users enjoy high-end features as customizable, free voicemail which is conveniently sent to you via email, free conference calling, free call forwarding, complete call history, free access to millions of people on SIP-based networks, built-in instant messaging (IM) capabilities,...
http://www.gizmoproject.com/GizmoDownload/WinGizmoInstall.exe - 10Mb - Download - Screenshot

sharpVoice(tm) Client
sharpVoice (formerly CyberTalkOnline) is a mature, reliable internet telephony program that enables free PC-to-PC and inexpensive PC-to-Telephone voice conference calls. sharpVoice Version 6. 0 offers great sound quality even over slow internet connections and the ability to conduct multi-person... Then you must register to make multi-person conference calls, PC-to-Phone calls, and to avoid advertising. ... Fully functional and ad-free for 30 days. ... Contains no SpyWare. ... Network-friendly design lets you make and receive calls even if you use a firewall or proxy server.
http://www.sharpvoice.com/download/sV6Setup.exe - 1Mb - Download - Screenshot

vPhonesoft
vPhone is a feature-rich VoIP Internet-Phone software. vPhone customers can download for FREE and talk to each other by voice or video calls, including multi-participant conference calls, send SMS, MMS messages from vPhone to vPhone and from vPhone to any e-mail, completely free! ... Additional features of vPhone allow our customers calling regular and cellular phones worldwide at great rates, sending SMS messages to cellular phones, a built-in answering machine with Web access, and all these exciting features: Voice call PC to PC, Voice call - PC to regular phones, Voice conference - 1+4...
http://www.virtualiphone.com/vPhoneSetup.php - 3b - Download - Screenshot

3CX VOIP Phone for Windows
Free VOIP / SIP phone. Use your PC as a phone. Works with any SIP / VOIP provider/ phone service. Use instead of the soft phone provided by your VOIP provider which locks you into their VOIP phone service. Easy to use interface includes dial pad and buttons to transfer or forward a call. ... Features include * Integrated phone book (allows you to assign caller ID to a name) * Supports several SIP profiles * Displays caller ID * Individual ring tones (per caller) * Drag & drop handling * Call log * Incoming calls: identify, accept, reject or ignore * Record phone calls * Multiple calls...
http://www.3cx.com/VOIP/3CXPhone.exe - 1Mb - Download - Screenshot

LetsPowwow Collaboration Software
LetsPowwow Collaboration Software is a free online communication, online meeting, and online collaboration tool for individuals and large groups. Because LetsPowwow is software agnostic, users can fully collaborate across Windows, Mac and Linux with any application using their Web browser. ... Team members communicate instantly online through public chat or via free conference calling. ... It's like they have their very own virtual conference room; ideal for creating, presenting, teaching, or training regardless of distance or physical barriers.
http://letspowwow.com/letsPowwow%20Free%20Online%20Meetings.exe - 3Mb - Download - Screenshot

PC-Telephone
Make FREE pc-to-pc, pc-pc and cheap pc-to-phone, pc-phone, pc-to-fax, pc-fax, phone-to-pc, phone-pc, fax-to-pc, fax-pc calls over Internet/VoIP or ISDN/PSTN telephone networks. Use your computer as internet telephone, USB phone, USB handset, ISDN telephone, ISDN fax, answer phone, fax software,... Works with all Firewalls, NAT and LAN routers - nothing to configure.
http://www.pc-telephone.com/download/pc-telephone.exe - 1Mb - Download - Screenshot

VoIPerized
VoIPerized is a so called VoIP (Voice over IP) program. VoIPerized enables you to make free audio calls to other people who also run VoIPerized. When making VoIPerized the focus was to minimize the latency, because other VoIP programs always seemed to have an irritating lag which makes the... 120 seconds + ping time) - Conference with unlimited people at the same time - Contact list supports unlimited number of contacts - Adjust the bitrate to your needs - High audio quality (16 kHz sampling) - Low CPU usage - Adaptive Jitter Buffering - Smart packetloss concealment - VAD (Voice...
http://www.student.tue.nl/m/j.s.d..../voiperized/voiperized24setup.exe - 316Kb - Download - Screenshot

IPi Phone
IPi Phone is internet IP to IP telephone software that allows you to talk and use text chat. IPi Phone is easy to use. All you need to know is the other person IP address and you can connect to them and start talking over the internet for free. You can use secure communication and voice... Communication can be encrypted with AES (160 bit key length). ... It allows you to keep your privacy and stay anonymous.
http://www.aolej.com/files/ipiphone.zip - 684Kb - Download - Screenshot

Blaze Audio Voice Cloak
Wouldn't it be fun if you could change your on-line voice into something completely different- change male to female and vice-versa, or even have a voice straight out of the latest science fiction movie? Now you can disguise, morph, and improve your online voice. ... At best of all, Voice Cloak is affordable, easy-to-use and comes with lifetime FREE product upgrade. ... Then you can use that preset any time you want to "be" that character. ... You can click on a button to add a funny sound effect in the middle of any conversation.
http://mirror.blazeaudio.com/downloads/VoiceCloakTrial.exe - 2Mb - Download - Screenshot