<p>I think the title pretty much says it all... I'm looking to implement an interface similar to the standard OS X sidebar used in all the above mentioned programs, and I'm wondering if anybody has any thoughts as to the easiest way to do it, namely about what view to use for the left hand selection pane. Really I don't think I even need the hierarchical component as seen in the apple apps, I just need a good looking flat list of choices which determine what's shown in the right hand pane.</p>

<p>The obvious start is a vertical split layout view, but beyond that I'm not entirely sure where to go. A collection view with only one column or something like that?</p>

I've done a few applications that use a similar setup.
I generally use an NSSplitView, with a single column NSTableView in the left pane.  Don't forget to disable the headers, and make it display as a "Source View" style.
If you want the disclosure triangles, then you'll want to use NSOutlineView instead of NSTableView, but at least for the first go, I'd stick to a simple NSTableView.
A pattern I also use is to make the NSTableView slightly shorter than the NSSplitView, and have buttons at the bottom (add, delete, etc).  I've usually built the program around Core Data, so it's easy to hook up these to methods to create/delete objects, and then bind the NSTableView to the array of objects.