Traffic Server is fast, scalable and extensible HTTP/1.1 compliant caching proxy server. Formerly a commercial product (created by Inktomi, later acquired by Yahoo!), it is now being developed as an Apache Incubator Project

A Tor-like p2p network of anonymizing traffic proxies. Aims to be easy to use and provide incentives for exit nodes

apt-cacher.pl is a CGI which will keep a cache on disk of Debian Packages and Release files (including .deb files) which have been received from Debian distribution servers on the Internet. When an apt-get client issues a request for a file to apt-cacher.pl, if the file is already on disk it is served to the client immediately, otherwise it is fetched from the Internet, saved on disk, and then served to the client. This means that several Debian machines can be upgraded but each package need be downloaded only once.

nginx [engine x] is a HTTP server and mail proxy server

A proxy server is a kind of buffer between your computer and the Internet resources you are accessing. They accumulate and save files that are most often requested by thousands of Internet users in a special database, called “cache”. Therefore, proxy servers are able to increase the speed of your connection to the Internet. The cache of a proxy server may already contain information you need by the time of your request, making it possible for the proxy to deliver it immediately. The overall increase in performance may be very high. Also, proxy servers can help in cases when some owners of the Internet resources impose some restrictions on users from certain countries or geographical regions. In addition to that, among proxy servers there are so called anonymous proxy servers that hide your IP address thereby saving you from vulnerabilities concerned with it.