hebig.org/blog
Personal webnode of Haiko Hebig

"If you maintain a web calendar, the vCalendar/iCalendar specifications can help you share calendar events with users through your site. By clicking on a simple link to a text file, your events can be added to your users' Outlook, Palm Desktop, or scheduling program of their choice. Such an application can be easy, simple, and automated if the event data is stored in a database, and the text file is formatted to the vCalendar/iCalendar specification with any scripting language.

The vCalendar and iCalendar specifications are designed for platform and device neutral sharing of calendar and to-do items. Since its inception, the vCalendar specification has quietly gained ubiquitous support in software applications and spawned its successor, the iCalendar format. Recently, iCalendar gained a big endorsement by being used to power Apple's iCal program."

phpbuilder.com
USING PHP TO MAKE BASIC vCALENDAR/iCALENDAR EVENTS
"In this article, I will run through the basic script setups needed, give a basic introduction to key vCalendar elements, and use PHP to format an example event. By the end, you should be able to share your calendars online."

PHP iCALENDAR
"PHP iCalendar is a php-based iCal file parser. Its based on v2.0 of the IETF spec. It displays iCal files in a nice logical, clean manner with day, week, month, and year navigation, printer view, RSS-enabled, and searchable. It supports 12 languages, is fully theme-able, and has complete timezone support."

Simon Wilson's Weblog
iCAL REFERENCE LINKS
"Mainly for my own reference, here are the sites I've trawled through investigating using the iCal standard as the file format for storing events." Contains links to all references one might need.

Zend
BUILDING A CALENDAR INTERFACE WITH PHP
"In this article we'll create a calendar mechanism, using PHP, MySQL, XHTML and CSS. When we're through, our calendar design will include PHP functionality capable of dynamically creating calendars and building linking to events stored in a MySQL database."