The Office Quick Access Toolbar
I used to hate the Microsoft Office "Ribbon" user interface. I still do, I suppose, but after six or seven years I've just gotten used to the fact that some of my favorite features from earlier versions have gotten separated from one another and kind of buried under different tabs.
Enter the Quick Access Toolbar. Located at the uppermost left corner of your Office application windows are some tiny icons, off by themselves and easily overlooked.
Not only are these icons small but they are (by default anyway) extremely boring: Save, Undo, Redo.
Many of us already have these functions locked into muscle memory as keyboard shortcuts (Ctrl-S, Ctrl-Z, Ctrl-Y), so we can just ignore that part of the window completely, right? Wrong!
This section of the user interface is totally customizable. If you don't like that Excel's Insert Chart function is buried deep in the Ribbon, unbury it! Ditto for Sort Data or any other function that you need 10-100 times per day in your workflow.
To customize this Toolbar, click the small black triangle to the right of its icons to expose the customization menu. Some of the most common (most boring) functions are included right in the menu so you can just turn their shortcuts off or on right there. To get to the good stuff, choose More Commands... to open a window that lets you add shortcuts for just about any part of the user interface. You can also open this window by choosing File => Options => Quick Access Toolbar.