Cocoa left column menu

Several mac applications, both Apple and third party, feature a menu in the left column usually used for filtering content. Below are some examples from iPhoto, iCal and iTunes. I don't see an interface builder class that corresponds to this. How are these usually implemented? A NSTableView with custom cells? Is there any pre-written code to handle the more complex aspects like the collapsing triangles? This seems like a such a common user interface that I don't want to reinvent the wheel if I don't have to.