If you run the spelling checker on your Excel worksheets (a good idea, even if you are an expert speller!), you might think that you have to run it separately for each worksheet in your document. But there's a simple way to spell check all of the worksheets at once, and it works in both Excel 2007 and Excel 2010.
Just right click one of the worksheet tabs and choose Select All Sheets:
If you'd rather select only specific worksheets, use the Ctrl key and click the tabs for the sheets you want to include.
Now click the Spelling button on the Review tab or just press the F7 key to save even more time.
Just be sure to right click the tab again and select Ungroup Sheets when you're done, or any changes you make to one worksheet (beyond spell-check edits) will be reflected on all that you have selected!