NOTE: The Fast View feature, while still available, has effectively been subsumed by the new minimize behavior (which places minimized stacks into the trim where they subsequently work by showing views in the same manner as the Fast Views). While there's only one Fast View Bar you can have as many minimized stacks as you want and can place them where you want in the trim. See 'Maximizing a view or editor' for details.
Fast views are hidden views that can be quickly opened and closed. They work like other views except they do not take up space in your Workbench window.
Fast views are represented by toolbar buttons on the fast view bar, which is the toolbar initially on the bottom left of the Workbench window. When you click the toolbar button for a fast view, that view opens temporarily in the current perspective (overlaying it). As soon as you click outside that view or the view loses focus it is hidden again. The fast view bar can also be docked on the other sides of the Workbench window.
By default the fast view bar is always visible. You can use the General > Perspectives preference page to hide the fast view bar if it is empty.
You can create a new fast view by dragging any open view to the fast view bar or by selecting Fast View from the menu that opens when you right-click the icon of the view's tab. You can also click on the left-most button of the fast View bar to open a menu which will show a list of views. Selecting a view from this list (or from the dialog that appears if you select 'Other...' will result in the selected view being added to the fast view bar and activating (i.e. shown as the active part).
Creating fast views
Moving and docking views
Maximizing a view or editor
Fast View bar