Perrin Harkins and Bill Hilf thoroughly documented how eToys was built, using Apache and mod_perl. This is a detailed description of how to build a multimillion page view site, with a lot of good insights.
The kicker is that the paper was written circa 2001, about 3 years ago. And in fact, being a retrospective, many of the ideas had been deployed a bit earlier. Of course, a lot of it is reiteration of stuff Philip Greenspun wrote about. In any event, this is now pretty much mature technology.
Via Ryan Tomayko.