Warning! This is a hack.
Mac OS X 10.5 Leopard ships with a pretty good version of PHP5 and an excellent version of Apache2. (It also ships with Ruby, Python and Perl.) Sounds like a decent FOSS development platform, doesn't it?
It's close, but not quite there, for my purposes and those of most developers I know. Why? No database.
Easily solved, you might say. Indeed, dropping a pre-packaged MySQL install into Leopard is easy and clean. But...
And you knew there had to be a catch, right? Else, why would I be writing this?