Is a clone of: http://drupal.org/sandbox/tim.plunkett/1427994 but adds some stuff:
- edit functionality for calendar items in overlay
- adds ctools overlay styles (is working but not configurable)
- optional hiding of some elements like publishing options etc.
it's only working for nodes and timplunkett will release a module soon which will have similar functionality but with a more generic approach (load all entities in the overlay not just nodes)