Open source caching Web proxy for offline use and low-bandwidth connections. Supports ad blocking and security filtering.

InterGate software offers web caching, stateful inspection firewall, content filtering and network management services. Anti spam module also available. [Mac OS, Windows]

IRC proxy, access control available via standard Unix hosts file configuration. [Linux]

A light-weight customizable HTTP proxy daemon. Free software licensed under the GNU GPL. [POSIX]

HTTP proxy that enhances user privacy by deleting (or faking) eight data elements, including the Cookie field and Referrer fields, from web browser responses. [Windows]

Filtering HTTP proxy that rewrites the HTML of the web pages that pass through it; removing unwanted/hostile content from the pages and providing enhanced user anonymity. [Written in PHP, platform independent]

HTTP/HTTPS proxy that runs from inetd, and uses less than 1kb of diskspace. [Unix]

ComTun Pro, offers connection sharing, firewall, spam filtering and caching. [Windows]

Offers connection sharing, monitoring and user level access control. Also offers http, email, ftp and news server functionality. [Windows]

Forwarding, non-caching, HTTP proxy targeted for traffic optimization. This open source application works by compressing pictures and other data.[UNIX]