Yes, Google is slowly taking over our entire Web lives. Google Calendar has just been launched and is a very slick and useful online calendar that will integrate with iCal, alert you via pop up, email and probably various other means, and generally be a damned handy online event tracking and calendar tool.
For the paranoid, you can make only certain calendars shared, just like iCal.
I also signed up to the New Zealand holidays calendar, which inserts all the NZ holidays onto the appropriate days. Unfortunately, the maker of that particular calendar didn't think to put international holidays like Easter or Christmas, but there will be other NZ holiday calendars you can subscribe to that will do that properly.
Now I just need a couple of friends who are web-savvy enough to get their own Google calendars working and experiment with sharing…