Echoplexus!

RetroShare is a open source cross-platform, private and secure decentralized communication system. It lets you to securely chat, share photos, videos, and more, using OpenPGP to authenticate peers and OpenSSL to encrypt all communication.

HipChat is an instant messaging service designed for companies and teams. It has persistent chat rooms, one-to-one chat, searchable chat history, file sharing via drag & drop and clipboard, inline image previews, an API, chat over SMS, and more.

Bitmessage is a P2P communications protocol used to send encrypted messages to another person or to many subscribers. It is decentralized and trustless, meaning that you need-not inherently trust any entities like root certificate authorities. It uses strong authentication which means that the sender of a message cannot be spoofed, and it aims to hide "non-content" data, like the sender and receiver of messages, from passive eavesdroppers like those running warrantless wiretapping programs. If Bitmessage is completely new to you, you may wish to start by reading the whitepaper. »

An IRC client for the Windows desktop which follows the Metro design guidelines.

TokBox makes it easy to add video chat to your site or mobile application using either the OpenTok API or OpenTok Widgets. Supports WebRTC.

A free, open-source, out-of-the-box audio conferencing app exposed via an API. Talk with your teammates, friends, and others at the push of a button.

Flowdock is a beautiful group chat. You can upload files, paste blocks of text, use #hashtags to make notes or create lists and mention others’ names to get their attention.

Simple & smart phone system designed for teams- Get numbers instantly wherever you need them. In 40 countries.- Cascade easily phone calls across your team, wherever they are, on any device- collaborate on calls: share contacts, comments, voicemails to make sure your customers are attended

Hyphen is an inter-company messaging app that allows businesses to instant message each other. Start building relationships, not just connections. We provide a network to connect businesses and professionals across all industries whether it's to an individual, team or entire business.

Collabe is an ideal tool for any company size or industry and is quite effective in really boosting your collaboration efforts, resulting in significantly improved efficiency and productivity of your team members, as individuals and as a collective. The software focuses on driving productivity and efficiency by ensuring that the 3C’s of productivity is well covered and maximized – coordination, collaboration, and communication.

jTorchat stands for Java Torchat, and is a complete rewrite of the popular p2p IM messenger Torchat