It really depends on your benchmark for "simple". With OS X Server, you have a lot of choices:
- Use WebObjects, if you want to leverage your skills with Objective-C (or even Java, for that matter, if you know Java).
- Use PHP... Apache and PHP are built in.
- Use Python and Django/TurboGears/Twisted/Plone/WSGI/ModPython.
- Use Ruby and Rails.
- Use Perl and CGI... or any language and CGI, for that matter.
- Use Java and Tomcat.
- Use Java and Tomcat + JBoss.
It's both a blessing and a curse, in your case, that OS X Server supports almost anything. Heck, you could almost even patch CGI to AppleScript if you wanted to (aside: I'm sure we both just cringed at that :-) ). There are a lot of built-in, free, options with OS X (Client) and OS X (Server).
PHP may seem your easiest choice for the default install of Apache and its configuration, but Ruby/Rails or Python are almost as readily available out-of-the-box.