If you have multiple files open the easiest way to close them all at once is to hold down the Shift key as you click on the File menu. When you do this the Close command changes to Close All which allows you to close all the open workbooks.

Bad news- it doesn't work in Excel 2007!!

Navigating
Pressing Ctrl+End takes you to the bottom cell of the worksheet you are in. This is a quick way to get to the end of your spreadsheet.

• Unfortunately if you have deleted some rows or columns and press Ctrl+End, Excel will still take you to the original bottom cell until you save the file.
  Once you save the file, Excel recalculates and determines where the new bottom cell is.
   

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Shift Key
This allows you to select large areas of data at once. It is a great shortcut for selecting, formatting or even copying.