A post on TUAW pointed me towards Google Calendar – it's just fantastic.
Now, I really only have experience with Outlook's Calendar functionality, which I used pretty heavily in 2002, 2003, and 2004 (and some of 2005) when I was sitting in the office at Massey all day. Since I switched to working at home I've intended to start using iCal, but just haven't got around to it, and since these days I do most of my work on a Windows laptop, that isn't an ideal situation anyway.
I'm also using gmail more and more [does anyone still need invites these days? I have heaps] for mail that I do want to interupt me, and leaving the browse-at-leisure mail to be processed with Mail (which does get a copy of all the gmail mail, as a backup). So gmail is open in Flock most of the time.
So I can see myself using Google Calendar (gCalendar, TUAW calls it) quite a lot, especially if a little calendar turns up in gmail next to the (unused by me, at this point)
chat box.
The interface is great – my connection is only 64Kbs at the moment, and it's still pretty smooth. All the niceties that you expect from a Google product are there. Try it out yourself!