Another take at ERCalendar. This time, it's using iCal4j to generate the data, so you can use all of the 
available APIs from iCal4j to extend it to your needs.

Sample call to create your calendar data:

  public WOActionResults createCalendar() throws URISyntaxException, SocketException, ParseException {
    ERCalendar calendar = new ERCalendar();
    
    java.util.Calendar startTime = GregorianCalendar.getInstance();
    java.util.Calendar endTime = GregorianCalendar.getInstance();
    endTime.add(java.util.Calendar.HOUR, 2);
    
    EREvent event = new EREvent(calendar);
    event.setClassification(Classification.PUBLIC);
    event.setDescription("Long description/note");
    event.setEndTime(new NSTimestamp(endTime.getTimeInMillis()));
    event.setFreeBusyStatus(FreeBusyStatus.BUSY_TENTATIVE);
    event.setLocation(new Location("Montreal"));
    event.setOrganizer(new Organizer("probert@macti.ca"));
    event.setCategories("Category 1, Category 2");
    event.setPriority(Priority.HIGH);
    event.setStartTime(new NSTimestamp(startTime.getTimeInMillis()));
    event.setStatus(EventStatus.CONFIRMED);
    event.setSummary("Title of the event");
    event.setTransparency(Transparency.TRANSPARENT);
    event.setUrl(new URI("http://www.wowodc.com"));
    event.addAttendee(new Attendee("probert@conatus.ca"));
    
    Calendar calendarData = calendar.transformToICalObject();
    ERPublishCalendarPage nextPage = (ERPublishCalendarPage)pageWithName(ERPublishCalendarPage.class);
    nextPage.setCalendar(calendarData);
    return nextPage;
  }