Circa 2006, I was developing a new website for our Linux Users Group at the University of Alberta, Liberating Students Digitally, using WordPress and we needed an events page. I figured I'd just create a Google calendar and there would be a WordPress plugin to display stuff from it. There was, Wooglecal, but it relied on Google's RSS feed, which means they don't have much control over the content and formatting of the events.
I don't use this code anymore. It might not work with WordPress, and it might have a horrible security hole. No guarantees.
There is a similar, but better maintained, plugin here.
Formerly GPLed. Now under the MIT License.
Wordpress version: Unzip the plugin into your plugins directory. Activate it in the Site Admin. Put [iCal:URL] into a post or page (where URL is the URL to your iCal file) and your events should magically appear in that post/page
Standalone version: Replace "Your URL Here" in the code with the URL to your iCal file. Style as you see fit.
Engine: The code is (sort of) commented.
Latest version: 0.31