At my place of employment, we use the Squid package to provide proxy caching of web pages. Squid offers high-performance caching of web clients, and also supports FTP, Gopher, and HTTP requests. In addition, Squid can be hierarchically linked to other Squid-based proxy servers for streamlined caching of pages.
There are two versions of Squid currently available. One, the "regular" version, seems to work well on machines with lots of RAM. The second version, "SquidNOVM" is suitable for machines with less RAM (I recommend using this version if you have 64 MB of RAM or less). Basically, the "NOVM" version uses less memory at the expense of more file descriptors. It's the one I use, and it works well.
( Under construction :-p )
To keep up with new features and bug-fixes, it is a probably a good idea to upgrade the Squid server from time to time. More information on Squid can be found on web site at http://squid.nlanr.net/Squid/.