Cozi Central looks like a pretty interesting site. This site is targeted towards families to help organize schedules and communication. Cozi Central reminds me of the next generation of the 3Com Audrey, which we had one of.
On Cozi Central you can see and edit the calendars for each family members. This will help you find times to make appointments for multiple family members. Also you can use the site to send messages to each other. You can configure the messages to be sent through SMS or email.
Cozi also lets you share and manage shopping lists. This in itself is not that interesting, but when you are away from your computer, you can have the list read to you or sent to you as a text message.
You can also sync these calendars with Outlook on Windows