OmniGraffle Version 5 deploys something called the Expando-collapso technology. This is basically a very nifty way of getting access to more functionality on limited screen real estate.
To the right of the tools palette, you see a bar with a rectangle making up an arrow. This widget is called the expando-collapso technology. Clicking on this arrow expands the toolbar. This is the expando part of the technolgy.
You'll notice that the arrow has now changed direction, and clicking on the arrow once more contracts the canvas toolbar into its original form with only the four basic tools available. This is the collapso part of the technology.
Big parts of this chapter are devoted to these tools. The tools are, from left to right: the Pen Tool, the Diagramming Tool, the Style Brush Tool, the Rubber Stamp Tool, the Magnet Tool, the Zoom Tool, the Move Tool and the Action Browse Tool.