Export Families to RFA Files (By Category)
Revit can export families to a library, but the control that you get is less than sufficient for large models. This exporter will organize your families into subdirectories matching the names of the category that the family originated from.
Reusable and Sharable Selection Sets
This amazing time saver will allow you to save a list of ElementID's for all selected objects to various text files. You can later call these selections back up and reapply them in your model. There is no limit to the number of elements that you can have selected nor the amount of separate selection sets that you can save.
You can also share the selection set text file with anyone on your design team.
Extrude Rooms to 3D Mass
This tool will extrude the boundaries for each room in your model to a 3D mass as a separate conceptual mass family and load it into your model placed exactly where the room is.
Update 5/8/2016: CASE and the CASE Apps website are no more but, courtesy of WeWork, the CASE Apps are now open source. They may be accessed on GitHub.