Squid is a high-performance proxy caching server for web clients,
supporting FTP, gopher, and HTTP data objects. Unlike traditional
caching software, Squid handles all requests in a single, non-blocking,
I/O-driven process.

Squid supports SSL, extensive access controls, and full request logging.
By using the lightweight Internet Cache Protocol, Squid caches can be
arranged in a hierarchy or mesh for additional bandwidth savings.

WWW: http://www.squid-cache.org/