If you have an Excel spreadsheet that you want to re-use without all of the data (say, to share with colleagues or use as a generic input form), you'll want to keep all of the formulas and text fields intact but clear the input values.
The quickest way to do this is with the Go to Special command, which is tucked under the Find & Select button on your Home tab in Excel 2007 and Excel 2010:
Now select Constants and then uncheck everything except Numbers in the list below it:
Now just press the Delete key to remove all of the values. Check that only the data you wanted was deleted - you can always Undo (Ctrl-Z) if it's not right and try again.
If you do want to remove Text fields, you could simply leave this box checked. You'll also no doubt note the other options available in the versatile dialog box displayed above - there's a lot of power in Go To Special command!