The first concept (interface) cries out for a service contract model to attach a UI package to calendar storage packages, one of which we might provide in the OpenACS toolkit but which might be provided by standard calendaring software instead. Fulfill the service contract, and the user doesn't care who is doing it.
The second notion is pretty much what Ben and I had talked about several months ago - you should be able to attach calendars to objects and arbitrary objects to calendars.
