In Microsoft Excel and OpenOffice Calc you can use the functions UPPER (), MINUSC () and PROPERNAME (the latter converts the first letter of each word to uppercase).
Suppose you want to put in lowercase all data in column A. First, add a column. Next, enter the formula = MINUSC (A1) in the first cell and copy it across the entire column. Then copy the entire column and paste it into the column A. For the latter, click Paste > Paste Special > Values (in Excel) or Paste Spatial > String(in Calc). Delete the column you created.