Telephone!

Linphone is an internet phone or Voice Over IP phone (VoIP). With Linphone you can communicate freely with people over the internet, with voice, video, and text instant messaging. Linphone makes use of the SIP protocol, an open standard for internet telephony. You can use Linphone with any SIP VoIP operator.

Nimbuzz offers limited availablility free calls and limited availability free text messaging for users via 3G and WiFi. Calls to other Nimbuzz users are free. PAY to call mobile or landline phones for as little as $0.02/minute in bulk with NimbuzzOut. Free SIP to SIP calls.

What does it do:

MicroSIP is a free portable SIP softphone for Windows based on PJSIP stack. It allowing to do high quality VoIP calls (P2P or on regular telephones) via open SIP protocol. From cloud of SIP providers you can choose best for you, register account and use it with MicroSIP. You'll get free p2p calls and cheap international calls.

3CXPhone is a free VoIP phone available for Windows, iPhone or any Android based smart phone such as Google Nexus, Sony Xperia, Motorola Droid or Samsung Galaxy. Connect 3CXPhone to a VoIP provider or to a VoIP PBX (for example 3CX Phone System) to make calls to any VoIP, mobile or landline number.

Combining voice calls, video calls and Instant Messaging in a simple interface, CounterPath's X-Lite helps you seamlessly transition from a traditional phone environment into the world of Voice over IP.

Paltalk is an instant messaging service that enables users to communicate via internet chat, voice and video chat. It offers chat rooms and the ability for users to create their own public virtual chat room.

YateClient is an Instant Messenger and a SoftPhone.

Chatzy is a free private chat service which you can use to communicate with people you already know or people who visits your blog or website. With Chatzy you can create a chatroom and send out email invitations very quickly and easily. No registration is required.

Starfish PBX aims to be an open source alternative to Digium’s Switchvox. The goal is to have a software equivalent to which we can add additional functionality like:

GV Connect is an unofficial iPhone/iPod Touch application for Google Voice. It stores your account password securely in your device's keychain for faster logins - communication is done via secure connections (SSL) to the Google Voice servers and no contact information is sent to Google. All operations are fully synchronized with your Google Voice account.