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.
The Shrew Soft VPN Client for Unix is a free IPsec Client for FreeBSD, NetBSD, and Linux based operating systems. It can be used to communicate with systems running ipsec-tools. The Unix client utilizes the IPsec kernel support included with the operating system, and comes with the complete Internet Key Exchange daemon and client front end application source code. A Windows version is also available.
mxallowd is a daemon for Linux Netfilter (using libnetfilter-queue) and BSD pf (using pflog) which implements a slightly improved nolisting mechanism. It requires your name server to be configured to return two MX IP addresses, and the one with higher priority must not run a mail server on port 25. mxallowd blocks attempts to connect to the mail server unless the sender tries to connect to the first mail server before the second. Since most spammers will attempt direct connections to each mail server, they will be blocked.
Callweaver is a community driven software PBX project. The most important differences between Callweaver and Asterisk are built-in STUN support, the use of SpanDSP for better codecs and full T.38 fax over IP support, Sqlite instead of Berkeley DB, universal jitterbuffer, POSIX timers to avoid Zaptel timing dependencies, greater speed, more efficient dialplan execution, and greater stability.