Google Calendar is released! It looks pretty promising, but I will not use this for my daily workflow. However It seems useful for keep track of different public calendar (such as subscribing myself to FIFA World Cup timetable, Australian holidays, and holidays for my team members etc). Make sure you take a look.
If google at some point supports syncing with both iCal and Outlook, and dare I hope for PDA & Cellphones then it will truly have a winning web-app on its hands as your calendar will be integrated across your entire PAN