If you never tried to use Google Calendar, you better try it out. It is the best web-base calendar i ever seem. G-Cal has rich functionalities and very user friendly. You can resist to use it once you get start.
One function I just discovered about G-Calendar is that,you can subscribe it to your ICal in Mac. Cool right? I have thought about this idea long time ago. Now seems dreams has come true. So here is an article teach you how to subscribe it toyour ICal:
http://www.tuaw.com/2006/04/13/howto-subscribe-to-a-google-calendar-using-ical/

One problem with it though, is it only one way transfer (G-Cal to I-Cal), once your subscribe it to your I-Cal, all event from G-Cal is read-only. But anyway, even though it is only one way transfer, it is good enough for me. I know google is working hard to get it to be syn with I-Cal, so keep your eyes on it.