Forum OpenACS Q&A: Re: aolserver caching and squid
I've never tried it, but I think normally you would never want to cache pages served from OpenACS by default in Squid, as many pages are customized for the user viewing them, and Squid presumably has no way to distinguish one OpenACS user from another. On the other hand, cacheing images or static content in Squid might be useful for some sites. (It might however be better just to serve that content separately with a different special purpose web server in the first place. The guys using AOLserver at AOL definitely do that.)
OpenACS uses AOLserver to cache all sorts of stuff, but it is probably all stuff a lower level than complete HTML pages, and then is used to assemble dynamically generated pages, which would make pretty distinct from anything you'd ever consider caching with Squid.
I think AOLserver's Fastpath code will cache the contents of static files in RAM, which would overlap to some degree with Squid-like cacheing, but I don't know whether Fastpath even works with OpenACS.