File Transfer:

PeaZip is a free, open source file and archive manager.

7-Zip is an file archiver program for windows. It supports packing and unpacking of 7z, ZIP, GZIP, BZIP2 and TAR format files and provides a better compression ratio than WinZip for ZIP and GZIP formats.

Dimdim is an open source web meeting product with features like Application, Desktop and Presentation sharing with A/V streaming and chat. No attendee installation – all features are available through a web browser. Dimdim can be integrated with Moodle.

WebHuddle is a simple, small, secure web conferencing on any platform that supports Java.

Colloquy is an advanced IRC, SILC & ICB client for Mac which adheres to OS X interface conventions. Colloquy has the look and feel of a quality Mac application.

KMess is a client to connect to the Microsoft MSN network, allowing you to chat with Windows Live Messenger users. It supports fast file transfers, display pictures, custom emoticons, and more.

Asterisk is the world’s leading open source telephony engine and tool kit. Offering flexibility unheard of in the world of proprietary communications, Asterisk empowers developers and integrators to create advanced communication solutions.

Mercury IM is a cross-browser Java MSN Messenger client. It is lightweight and customisable.

aMSN is an open source MSN Messenger clone, with features such as: display pictures, custom emoticons, multi language, webcam support, full-speed file transfer, chat logs, conferencing support, event alarms and more.

Adium is an instant messaging application for Mac OS X that can connect to AIM, MSN, Jabber, Yahoo, and more.

Miranda IM is an open-source multi protocol instant messenger client for Microsoft Windows. Designed to be resource efficient with a rich feature set, Miranda supports AIM, Jabber, ICQ, IRC, MSN, Yahoo and more.

Pidgin is a multi-protocol Instant Messaging client that allows you to use all of your IM accounts at once. It works with the following: AIM, IRC, Yahoo!, MSN, MyspaceIM, ICQ, Zephyr and more.

Open source Group Collaboration software for Enterprise and business usage. Combines the capabilities of collaboration tools like wikis, blogs, file repositories, micrologs instant discussions, other social applications into a seamless platform.

Cyberduck is an open source FTP, SFTP, WebDAV and Amazon S3 browser with an easy to use interface, integration with external editors and support for many Mac OS X system technologies such as Spotlight, Bonjour, Quick Look and the Keychain.

DC++ is a client for Windows for the Direct Connect network. Direct Connect allows you to share files over the Internet without restrictions or limits. The client is completely free of advertisements and has a nice, easy to use interface.

Deluge is a lightweight cross-platform BitTorrent client. Full-featured, it uses libtorrent in it’s backend and PyGTK for it’s user interface.

WinSCP is an open source SFTP client and FTP client for Windows. Its main function is the secure file transfer between a local and a remote computer. Beyond this, WinSCP offers basic file manager functionality. It uses Secure Shell (SSH) and supports, in addition to Secure FTP, also legacy SCP protocol.

ccPublisher will help you tag your audio and video files with information about your license and it allows you to upload Creative Commons-licensed audio and video works to the Internet Archive for free hosting.

Filezilla is one of the most popular Open Source FTP solutions available and it has recently undergone an upgrade. It is reliable software with a user-friendly interface. Highly recommendable.

A simple IRC client for Windows operating systems. Features coloured nicknames and alignment by text as opposed to by name.

SolarSeek is a SoulSeek peer to peer client for Mac OS X. Uses bindings and Cocoa to give a clean, powerful interface.

Tribler is an open source Peer-to-Peer feature packed client for watching videos online. It supports standard features such as key word searching for content and segmented downloading.

Shareaza is a peer-to-peer file sharing client which supports the Gnutella, Gnutella2, eDonkey Network, BitTorrent, FTP and HTTP network protocols and handles magnet links, ed2k links, Piolet links, and the now deprecated Gnutella links.

KTorrent is a BitTorrent client written in C++ for the K Desktop Enivonment (KDE) using the Qt user interface toolkit. It is maintained in the KDE Extragear.

FrostWire, is a super fast Gnutella Peer-to-Peer client with PRO connections from LimeWire PRO. It is spyware and adware free, includes iTunes integration, firewall to firewall transfers, Bit Torrent support and more…

Deluge is a lightweight cross-platform BitTorrent client. Full-featured, it uses libtorrent in it’s backend and PyGTK for it’s user interface.

Ares is a file sharing program that enables users to share any digital file including images, audio, video, software, documents, etc.

PeerGuardian 2 is an IP blocker for Windows that integrates support for multiple lists, list editing, automatic updates, and blocking all of IPv4, making it the safest way to protect your privacy on P2P.

Transmission is a lightweight yet powerful BitTorrent client with a simple, intuitive interface designed to integrate tightly with whatever computing environment you choose to use.

Gnucleus is a Windows application for accessing file shares on the Gnutella and G2 networks.

Azureus implements the BitTorrent protocol using java language and comes bundled with features such as multiple torrent downloads, advanced seeding, cache adjustment and more.

Emule is a reliable peer-to-peer file sharing client that features a queue and credit system, intelligent corruption control, file preview function, user categories, a wide file search array and much more.

Limewire is a fast and lightweight File Sharing program that supports Bittorrent downloads. It is spyware and adware free and works behind firewalls.