We have recently been considering using Moodle as a tool to help planning. We have not yet decided exactly what our spec. is, so in the meantime we are experimenting with using a wiki.
We have a course for the department teachers only - ie the Head of Dept is the 'teacher' and the other teachers are the 'students'.
There is a wiki with a front page containing the teachers' names each of which is a link to a page containing their timetable. Each class on the timetable is a link to a page where their lessons are recorded/planned. from there we have not finalised - perhaps each lesson will be a date as a link to another page with details, or perhaps the class page will contain a list of lessons as elsewhere on this discussion.
Screenshot of 'timetable' page below. Each page must have unique name so if classes are shared, or taught on same day then page name must include staff code. It is still early days so cannot tell how effective t will be. It requires trust as all can see each others classes/records - potentially good for sharing ideas etc, but less so if you have lazy colleagues or those who may screw up the pages of other staff accidentally.
Once we decide our proper spec. we may publish here to see if others are interested and something can be developed. We would need a system that is more robust than this wiki - but it is teaching us a new module that may then be used elsewhere with our students.