A fast PPTP proxy for any BSD with OpenBSD packet filter installed. It handles multiple transparent bi-directional tunnels, and can be chained from one proxy to another over several servers.
Auto ProxyFilter Test (APFT) automates the testing of safe and unsafe URLs against a content filtering proxy (such as Dansguardian) and helps prevent regressions. APFT is useful to people who are designing filter rules.
Crowd Control is an small, cross-platform HTTP proxy (a fork of the elhttp project) designed for systems with little RAM, such as a home router. It can filter URLs using SquidGuard blocklists, and has the unique ability to filter HTTPS domains as well.
Security proxy to clean up all unallowed constructions from HTTP requests, detect intruders and filter outgoing HTTP traffic against leaking classified data.
WaterFall project was started as a proxy/filter/firewall solution for NNTP (Usenet News) abuse protection. Due to the similiarity, SMTP may be covered as time permits.