If you right click the toolbar and click "Customize Toolbar," and then drag every item off of it, you can sort of hide it. The title bar won't be AS small as if you were to totally hide it, but it does still get about half as small.
Sure,
Choose Customize Toolbar from the View menu. Then drag all items off the toolbar.
And - voilà! - no toolbar! Sidebar remains in place if you like that.