So you want to use the Today function in a calculated list column.  Well here's a way to trick sharepoint into letting you use it, when it says it won't allow it.  First create a string cloumn named Today and save the list.  Now create a calculated column named GetDate and but Today as the calculated field.  Now we delete the today column and ta-da the GetDate column will always have todays date in it.  We do this so we don't have to keep adding the temp Today field every time we edit the list item with a calc field using the today function.  Now this is different from creating a data field and setting the date to current date, this date will stay set after it have been filled out.