Is there any way to share a calendar so that it's not read-only? I'd like my colleagues and I to be able to share and edit a couple calendars that affect us all. However, using the "Publish" option seems to make the calendars read-only, and since we all have different .Mac accounts (and some people don't have .Mac at all) I don't think we can use iSync. Is it possible to do what we want to do?