I just had the idea to implement an iCalendar feed in some application. And guess what? It's really piece of cake!

Create a XPage, set all properties -> rendered to "false", add some code like this into the afterRenderResponse event:
(don't copy and paste my code, it contains specific stuff for my app...)

---
var exCon = facesContext.getExternalContext();
var writer = facesContext.getResponseWriter();
var response = exCon.getResponse();
var nview:NotesView = database.getView("($plans)");
nview.setAutoUpdate(false);
var vc:NotesViewEntryCollection = nview.getAllEntriesByKey(@UserName(), false);
var ve:NotesViewEntry = vc.getFirstEntry();
var values;
var date;
var body;
var period;
var i = 0;
response.setContentType("text/calendar");
response.setHeader("Cache-Control", "no-cache");
writer.write("BEGIN:VCALENDAR\n");
writer.write("VERSION:2.0\n");
writer.write("X-LOTUS-CHARSET:UTF-8\n");
while (ve) {
        values = ve.getColumnValues();
        date = values.elementAt(5);
        body = values.elementAt(6);
        period = values.elementAt(2);
        writer.write("BEGIN:VEVENT\n");
        writer.write("DTSTART:"+date+"T080000\n");
        writer.write("DTEND:"+date+"T080000\n");
        writer.write("TRANSP:OPAQUE\n");
        writer.write("DESCRIPTION:"+body+"\n");
        if (period == "d") writer.write("SUMMARY:Plan für heute\n");
        if (period == "w") writer.write("SUMMARY:Plan für die Woche\n");
        if (period == "m") writer.write("SUMMARY:Plan für den Monat\n");
        writer.write("UID:"+values.elementAt(1)+"-ynplan\n");
        writer.write("END:VEVENT\n");
        ve = vc.getNextEntry(ve);
}
writer.write("END:VCALENDAR\n");
writer.endDocument();
---

You can subscribe to that feed with your Notes calendar, just click "add calendar", select "iCalendar" as format and set the URL to your XPage.
There is a lot of more stuff in the iCalendar format... if you need it, just export some calendar entry of your Notes calendar to iCal and have a look at the file.