Looking to set up a web server for my projects. Apache on Linux is free and dominates the web. IIS on Windows Server is proprietary but integrates with ASP and SQL Server.

What are people running? Is there a reason to choose IIS over Apache if I'm doing PHP?

Apache on Linux, no question. Free, stable, well-documented, and PHP runs natively. IIS is fine for ASP/.NET but Apache is the standard for PHP.

Apache 2.0 was just released with much better Windows support actually. But for production PHP hosting, Linux is still the way to go.