Wikipedia: "iCalendar is a standard (RFC 2445) for calendar data exchange. The standard is also known as 'iCal'."
I'm adding "iCalendar" to my Google, Feedster and Technorati searches which already cover "iCal."
I'm sure we'll be living with both terms in perpetuity. The Microsoft Windows Vista folks prefer "iCalendar," probably because Apple named a product "iCal." Outside of the IETF, I hardly ever heard "iCalendar" until Microsoft started using the name.