Multiple-User Calendar

I have a need to create a calendar that reserves a single room in a church hall; we allow people to sign up with paper & pencil if they would like to reserve the space, but would like to allow them to do this online from now on, on our church’s WordPress-driven website.

Are there any plugins that allow for this sort of behavior? Ideally, we’d like people to just add dates to the calendar without having to log into the WordPress admin interface.

Please help!