A series of the GNOME Shell screencasts can be found here.
First video starts off showing a regular workspace. It shows viewing the user menu available from the button on the right of the panel, viewing the menu for one of the tray icons, opening the Activities Overview by clicking on the Activities button on the left of the panel, and viewing the title of a particular window.
Second video shows how the Activities Overview can be used for launching new applications and opening documents.
Third video shows how new workspaces can be added in the Activities Overview, how existing windows can be moved between workspaces, and how new applications and documents can be launched on a particular workspace by being dragged there. While clicking an item launches it and exists the Activities Overview (as shown in the second video), dragging an item to a workspaces launches it, but keeps the Activities Overview open.
Fourth video shows how the applications view can be expanded. Entering a search term changes the applications results list, which can then be navigated by paging. Dragging an item from the list causes the workspaces to slide back in, returning the Activities Overview to the default state and allowing the user to drop the item on a particular workspace. The user then moves the newly launched application to a new workspace and switches to that workspace.
