Many calendaring programs (Outlook, iCal) support vCal for downloading event information and adding it to your calendar. Others can use the vCalendar microformat to extract data. Neither of these, however, seems to be supported on the iPhone.
Is there any functional equivalent that will allow me to list event information on a page and have a website visitor add the event to her calendar with a single click? Since Mobile Safari makes it super-easy to extract emails and phone numbers from web pages, it seems odd that there's no similar functionality for events.
As of iOS 5, if you create a http link to an .ics file, Mobile Safari will offer to open it up in Calendar.