A free alternative to Cold Fusion or ASP?

Ask most Web application developers their scripting language of choice, and you'll find that most are divided into two camps - the Microsoft Active Server Pages (ASP) folks, and the Cold Fusion users. If you do a little more research however, you'll find there are other options out there, and one of these, PHP 3.0, is in much wider use than one would think for an "alternative product".