Distributed Checksum Clearinghouse (DCC) is a system of clients and servers that collect and count checksums related to mail messages. The counts can be used by SMTP servers and mail user agents to detect and reject bulk mail. DCC servers can exchange common checksums. The checksums include values that are "fuzzy", or constant across common variations in bulk messages.
The GNU Gatekeeper is a free H.323 gatekeeper based on the OpenH323 project. You can use it to manage a Voice-over-IP network and let endpoints (e.g., Netmeeting) communicate through symbolic names. It also has an external interface for billing and other applications. It runs on a number of Unix versions (including Linux and Solaris) and Windows.
Quassel IRC is a modern, cross-platform, distributed IRC client, meaning that one or more clients can attach to and detach from a central core, much like the popular combination of screen and a text-based IRC client, but graphical. In addition to this unique feature, it aims to be a comfortable chatting program.
extract_url.pl is a Perl script that extracts URLs from either correctly-encoded MIME email messages or from plain text. It can be used either as a pre-parser for a URL selector (such as urlview), or as a standalone URL selector. It is very configurable, can handle URLs that have been broken over several lines in format=flowed delsp=yes email messages, and eliminates duplicate URLs. It was designed primarily for use with Mutt, but can be used by for any similar purpose. The idea is that if you want to access a URL in an email, you pipe the email to a URL extractor (like this one), which then lets you select a URL to view in some third program (such as Firefox).
DJIGZO Email Encryption Gateway is a centrally managed email server that encrypts and decrypts incoming and outgoing email at the gateway level. Djigzo currently supports two encryption standards: S/MIME and PDF encryption. The built-in Data Leak Prevention (DLP) module can be used to prevent certain information from leaving the organization via email. DLP can be configured to filter on credit card numbers, bank account numbers, excessive amounts of email addresses or other personal information in one email message, and more. DJIGZO can be installed on most Linux and Unix based systems. Installation packages are available for Ubuntu, Debian, Red Hat and CentOS. A ready to run virtual appliance for VMware and Hyper-V is available. An add-on for BlackBerry is available.
Kune is a distributed social network focused on collaboration rather than just on communication. It focuses on online real-time collaborative editing (Wave-based), decentralized social networking (federation), and Web publishing, while focusing on workgroups rather than just on individuals. It aims to create online spaces for collaborative work where organizations and individuals can build projects online, coordinate common agendas, set up virtual meetings, publish on the Web, and join organizations with similar interests. It has a special focus on Free Culture and social movements needs.