CalendarHome.com, for an abundance of free online calendars of all sorts. Print out plain monthly calendars. Create free photo calendars using pre-set collections of images--wildlife, astronomy, and the work of selected artists. View a 100-year perpetual calendar, or download a 1000-year perpetual calendar. Register for a personal web calendar.
You can even create your own calendar with your own photos (for a fee) or purchase calendars from the site's store.
A Date Calculator and a Calendar Converter are also available, as well as information about any date in history.