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.
Pen is a load balancer for "simple" TCP-based protocols such as HTTP or SMTP. It allows several servers to appear as one to the outside. It automatically detects servers that are down and distributes clients among the available servers. This gives high availability and scalable performance.
rsync is a replacement for rcp (and scp) that has many more features. It uses the "rsync algorithm" which provides a very fast method for remote files into sync. It does this by sending just the differences in the files across the link, without requiring that both sets of files are present at one of the ends of the link beforehand.
C++ Sockets is a cross-platform C++ wrapper for BSD-style sockets. It implements the TCP, UDP, ICMP, and SCTP transport layer protocols. Implemented application layer protocols are HTTP/HTTPS (using OpenSSL), SMTP (server), and Ajp/1.3 (server). Features include transparent SOCKS4 client support and asynchronous DNS. Included in the library are a number of HTTP client functions such as GET/PUT/POST, and also Web server framework components.
GNUnet is a peer-to-peer framework with focus on providing security. All peer-to-peer messages in the network are confidential and authenticated. The framework provides a transport abstraction layer and can currently encapsulate the network traffic in UDP, TCP, HTTP, HTTPS, or direct 802.11 (WLAN). GNUnet supports accounting to provide contributing nodes with better service. The services built on top of the framework include anonymous file sharing and a virtual network providing IPv4-IPv6 transition via protocol translation over the P2P network.
Ettercap is a network sniffer/interceptor/logger for ethernet LANs. It supports active and passive dissection of many protocols (even ciphered ones, like SSH and HTTPS). Data injection in an established connection and filtering on the fly is also possible, keeping the connection synchronized. Many sniffing modes were implemented to give you a powerful and complete sniffing suite. Plugins are supported. It has the ability to check whether you are in a switched LAN or not, and to use OS fingerprints (active or passive) to let you know the geometry of the LAN.
Cherokee is a very fast, flexible and easy to configure Web server. It supports widespread technologies including FastCGI, SCGI, uWSGI, PHP, CGI, SSI, TLS and SSL encrypted connections, virtual hosts, authentication, on the fly encoding, load balancing, Apache compatible log files, database balancing, reverse HTTP proxy, traffic shaping, video streaming, and much more. A user friendly interface called cherokee-admin is provided for no-hassle configuration of the server. It allows you to configure the server from top to bottom without editing a text configuration file.