The new Ribbon in Office 2007 can take a while to get used to, so the Quick Access Toolbar is a great way to put your most frequently used commands on a single toolbar while you are getting used to the Ribbon.

Open Excel 2007 and click the down arrow next to the Quick Access Toolbar.

From the menu choose More Commands…

Now highlight the commands you want to appear on the toolbar from the left column, and click the Add button to add them to the selected box on the right-hand side.

You can also check the box for "Show Quick Access Toolbar below the Ribbon" if you don't like the toolbar appearing in the title bar.

Notice the toolbar is now below the ribbon, and the items have been added to the toolbar.

This is definitely a simple tip, but I've found it's very useful.