A comprehensive list of Excel shortcuts is available as a PDF download.
By now, most Office users probably know the Bold, Italic, and Underline shortcuts as well as they know their own names. (I've included them here because someone will surely take me to task if I leave them out.) But the rest of these shortcuts are less well known, even though you might actually need to apply, say, the Currency format to data more often than Underline or Italic.
These are standard, practical shortcuts that can save you time in earlier versions of Excel -- but they're especially useful in Excel 2007. Although the formats are accessible from the Home tab in that version, it could be years, possibly decades, before you develop the habit of locating them quickly. And if you're working in a different tab, you don't want to have to keep switching back to the Home tab just to format the data you're working on.
|Bold the selection||Ctrl+B|
|Italicize the selection||Ctrl+I|
|Underline the selection||Ctrl+U|
|Strike through the selection||Ctrl+5|
|Open the Style dialog box||Alt+'|
|Open the Format Cells dialog box||Ctrl+1|
|Apply the General format||Ctrl+Shift+~|
|Apply the Currency format||Ctrl+Shift+$|
|Apply the Percentage format||Ctrl+Shift+%|
|Apply the Date format||Ctrl+Shift+#|
|Apply the Time format||Ctrl+Shift+@|
|Apply the Number format||Ctrl+Shift+!|
|Apply the Exponential number format||Ctrl+Shift+^|
|Apply an outline border to the selection||Ctrl+Shift+&|
|Remove an outline border from the selection||Ctrl+Shift +_|