#1 iCalendar (.ics) feeds for "to do" items

[Andrew Ziem]

It would be convenient to provide a person's to-do list
in iCalendar format for aggregation in PIM application
such as Outlook, Mozilla Sunbird, iPod, Google
Calendar, etc.

For reference, read RFC 2445 about VTODO
http://www.kanzaki.com/docs/ical/vtodo.html
http://en.wikipedia.org/wiki/ICalendar#To-do_.28VTODO.29
http://www.ietf.org/rfc/rfc2445.txt

As a sort of authentication, I suggest considering
generating special URLs with a long, random, secret
string. That's how Google Calendar provides access to
what it calls "Private URLs."