iCal : create links to web or files

TUAW summarizes an OS X Hints tip:

Create clickable URL/file events in iCal - The Unofficial Apple Weblog (TUAW)

All you need to do for a URL is either drag it (or its icon) from a browser's address bar onto a time slot in iCal, or add a URL to an event's title and surround it with carrots like this, sans-quotes: "." To create a click-able link to a file, you'll need to use a web browser (such as Firefox) to surf your file system, then simply drag a file or folder from the browser into iCal in the same way as a URL. Don't try it with Safari, as it apparently doesn't do local file/folder surfing.