AJAX Calendar addon for existing WordPress template

Looking for an attractive calendar addon. Addon is to feature one month past, current month, and one month in future. Features required: Require that there be a backend administration module allowing for adding, removing, editing of events by "admin" group users. Frontend should allow website visitors to easily roll over date and see brief two line description of events and click to view full event descriptions. This calendar will be the feature of the website so it will be the most critical element. Looking to integrate into an existing WordPress template if possible.