nsodc.eu wrote: Does anybody know the best way to build a business directory?
I want to show (nested) department members, but also a complete list of employees.
Preferably with a contact button like available in Native Joomla, so I can let guests fill out a contactform to contact a employee.
Community Builder was not designed to be a directory extension.
Suggest you look at sobi or mosetree.
You can have a department field in your CB profiles and then create various lists filtered on this field. See tutorials for CB List example.
nant