As lame as it may sound: a calendar.
PHP: Output the calendar into a table with PHP
MySQL: Select dates out of a MySQL database and for each date that has an event (in the database), provide a link for more information.
XHTML: Create the calendar in PHP with XHTML...add a template with content if you like with the calendar on the side.
DHTML: If you don't count AJAX as DHTML, have a function that displays all events for a day in a box when you hover over the date.
AJAX: Upon clicking on arrows next to the month name, change the calendar to the previous or next month.
For an example of this, check out a personal site I'm working on: brandonfrohs[dot]com. I don't have the calendar fully styled, but it gives you the basic idea. Oh, and visit it in FF. I haven't tested it in other browsers as of yet, and I know it won't work in IE.
A month late, but I hope it helps anyways!