FreeRADIUS is a high-performance, highly configurable, and feature-rich RADIUS server. Supported features include EAP (wireless authentication, PEAP, TTLS), MySQL, PostgreSQL, Oracle, LDAP, X9.9 token cards, VMPS, and many more. It comes with more than 50 vendor dictionaries, and interoperates with many others. It is the only open source RADIUS server that has implemented EAP, and it is currently deployed in multiple million-user systems.
Cyan Secure Web Proxy Server is a carrier grade, high performance Internet filtering proxy server for Linux. It includes scalable (user/group/host) Web filter and virus scan utilities for blocking malicious applications at the gateway. It has an advanced URL database, authentication support (Active Directory, LDAP, NTLM), SSL Interception, easy deployment, and remote administration.
squid_redirect uses a list of patterns to zap annoying ad banners from Web pages, inserting a placeholder image. It lives in a Web proxy and so requires no special browser facilities. It's readily customizable, small, fast, and easy to install. (In Debian/Ubuntu, this program is named "adzapper".)
Middleman is a robust proxy server with many features designed to remove unwanted content, increase privacy, and to simply make surfing the Web a more pleasant experience. Some of the highlights include banner and popup blocking, HTTP and FTP content caching, NTLM and Basic authentication when forwarding through another proxy server, regular expression substitution in downloaded files and HTTP headers, regular expression substitution on requested URLs, many URL commands to temporarily change the proxy settings or to view information about a requested file, complete support for HTTP/1.1 including persistent connections and gzip encoding, and an intutive Web interface for configuring the proxy.
MailStripper Pro is a mail scanner that aims to remove spam and viruses from incoming mail. It recognises and decodes many obfuscation techniques used by spammers and uses several different mechanisms to recognise spam which are immune to Bayes poisoning, and has achieved real-world success of over 99.8%. It is MTA-independent and does not implant itself into your mail server. Instead, it functions as a proxy, allowing the MTA to reside on a different server.
Ping Tunnel is a tool for reliably tunneling TCP connections over ICMP echo request and reply packets (commonly known as ping requests and replies). It is useful for evading firewalls that, for whatever reason, prevent outgoing TCP connections, but allow in- and outgoing ICMP packets. The tunnel works by having a proxy run on a machine ping-able from the inside of the firewall, with the client running on the local machine from which TCP access is required.
pacparser is a library to parse proxy auto-config (PAC) files. Proxy auto-config files are a vastly used proxy configuration method these days. Web browsers can use a PAC file to determine which proxy server to use or whether to go direct for a given URL. The idea behind pacparser is to make it easy to add PAC file parsing capability to any program (C and Python are supported right now). It comes as a shared C library and a Python module that can be used to make any C or Python program PAC scripts intelligent. Some very useful targets could be popular Web software like wget, curl, and python-urllib.
P3Scan is a full transparent proxy server for email clients. It runs on a Linux box with iptables (for port redirection). It can be used to provide email scanning from the Internet to any internal network, and is ideal for helping to protect your "Other OS" LAN from harm, especially when used in conjunction with a firewall and other Internet proxy servers. It is designed to enable scanning of incoming email messages for viruses, worms, trojans, spam, and harmful attachments. Because viewing HTML email can enable a spammer to validate an email address (via Web bugs), it can also provide HTML stripping.