I'm having the strangest issue since updating to OS X El Capitan. My "Open File" dialogs show the sidebar but all my main (and useful) locations are missing. Take a look at this screenshot. This screenshot shows Keychain Access but this happens in Safari when I'm trying to attach a file to Gmail for example, or uploading an image to Facebook.
What I would like is for the sidebar to show my home directories, such as Desktop, Documents, Downloads, etc.