Just came across AirSet and I like it! It's a shared calendar and contact application. Maybe there are a lot of them out there that compare favorably to this but I'm not aware of them. There are a couple of nice things:
1) it's calendar and contacts
2) you can set up multiple groups and have calendars for each of them
3) you've got a personal calendar which can show all of the appts from all of the groups
4) you can control what shows up
5) updates you make, regardless of whether it's on your cell phone or the web site, show up immediately in everyone's view
Update 6/12/2006: Just spoke with my brother and he told me about Planzo. Doesn't look like it does phone but I haven't really checked it out yet. GW Bush has a Planzo calendar here and so does Condi so it looks like they have a sense of humor.