Option for sidebar with tree (list) view?

[JayBrown]

I've been looking into Rixstep's Xfile software, and a good thing to have would be an (optional!) sidebar with a tree (list) view of the volume, drop down menus for quick navigation, toggle hidden files in sidebar (default on). There could possibly be a better way to access external volumes in the sidebar, instead of going through /Volumes/:

Screenshot of Xfile sidebar:

Note: migrated here from the magnumbytes forum

[singalen]

Might be a panel as well.