Squid is a full-featured Web proxy cache. It is free, open-source software, and the result of many contributions by unpaid (and paid) volunteers .
Squid supports proxying and caching of HTTP, FTP, and other URLs; proxying for SSL; cache hierarchies; ICP, HTCP, CARP, Cache Digests; transparent caching; WCCP; extensive access controls; HTTP server acceleration; SNMP; caching of DNS lookups.